diff --git a/Altair8800/altair8800_sys.c b/Altair8800/altair8800_sys.c
index 373f1bca..ad314c8a 100644
--- a/Altair8800/altair8800_sys.c
+++ b/Altair8800/altair8800_sys.c
@@ -73,6 +73,7 @@ DEVICE *sim_devices[] = {
     &mdsk_dev,
     &m2sio0_dev,
     &m2sio1_dev,
+    &acr_dev,
     &sio_dev,
     &sbc200_dev,
     &tarbell_dev,
diff --git a/Altair8800/altair8800_sys.h b/Altair8800/altair8800_sys.h
index 34a1b025..b5a1a225 100644
--- a/Altair8800/altair8800_sys.h
+++ b/Altair8800/altair8800_sys.h
@@ -47,6 +47,7 @@ extern DEVICE po_dev;
 extern DEVICE mdsk_dev;
 extern DEVICE m2sio0_dev;
 extern DEVICE m2sio1_dev;
+extern DEVICE acr_dev;
 extern DEVICE sio_dev;
 extern DEVICE sbc200_dev;
 extern DEVICE tarbell_dev;
@@ -60,7 +61,7 @@ extern int32 sys_find_unit_index(UNIT* uptr);
 extern void sys_set_cpu_instr(t_stat (*routine)(void));
 extern void sys_set_cpu_pc(REG *reg);
 extern void sys_set_cpu_pc_value(t_value (*routine)(void));
-extern void sys_set_cpu_parse_sym(t_stat (*routine)(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw));
+extern void sys_set_cpu_parse_sym(t_stat (*routine)(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw));
 extern void sys_set_cpu_dasm(int32 (*routine)(char *S, const uint32 *val, const int32 addr));
 extern void sys_set_cpu_is_subroutine_call(t_bool (*routine)(t_addr **ret_addrs));
 extern char *sys_strupr(const char *str);
diff --git a/Altair8800/mits_acr.c b/Altair8800/mits_acr.c
new file mode 100644
index 00000000..06b8fe62
--- /dev/null
+++ b/Altair8800/mits_acr.c
@@ -0,0 +1,245 @@
+/* mits_acr.c: MITS Altair 8800 88-ACR
+
+   Copyright (c) 2025 Patrick A. Linstruth
+
+   Permission is hereby granted, free of charge, to any person obtaining a
+   copy of this software and associated documentation files (the "Software"),
+   to deal in the Software without restriction, including without limitation
+   the rights to use, copy, modify, merge, publish, distribute, sublicense,
+   and/or sell copies of the Software, and to permit persons to whom the
+   Software is furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+   PETER SCHORN BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+   IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+   Except as contained in this notice, the name of Patrick Linstruth shall not
+   be used in advertising or otherwise to promote the sale, use or other dealings
+   in this Software without prior written authorization from Patrick Linstruth.
+
+   History:
+   27-Dec-2025 Initial version
+
+*/
+
+#include "sim_defs.h"
+#include "s100_bus.h"
+#include "mits_acr.h"
+
+#define DEVICE_NAME "ACR"
+
+static int32 poc = TRUE;            /* Power On Clear */
+static int32 rdr = 0x00;            /* Receive Data Register */
+static int32 rdre = ACR_RDRE;       /* Receive Data Register Empty Bit */
+
+static t_stat acr_reset      (DEVICE *dptr);
+static t_stat acr_attach     (UNIT *uptr, const char *cptr);
+static t_stat acr_detach     (UNIT *uptr);
+static void acr_rdr          ();
+static int32 acr_io          (const int32 addr, const int32 rw, const int32 data);
+static int32 acr_data        (const int32 addr, const int32 rw, const int32 data);
+static t_stat acr_rewind     (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+static t_stat acr_show_help  (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
+static t_stat acr_attach_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
+
+static const char* acr_description(DEVICE *dptr) {
+    return "MITS 88-ACR";
+}
+
+static RES acr_res = { ACR_IOBASE, ACR_IOSIZE, 0, 0, NULL };
+
+static UNIT acr_unit = {
+    UDATA (NULL, UNIT_ATTABLE | UNIT_ROABLE | UNIT_ACR_VERBOSE, 0)
+};
+
+static REG acr_reg[] = {
+    { NULL }
+};
+
+static MTAB acr_mod[] = {
+    { UNIT_ACR_VERBOSE,     UNIT_ACR_VERBOSE, "VERBOSE", "VERBOSE", NULL, NULL, NULL, "Enable verbose messages"  },
+    { UNIT_ACR_VERBOSE,     0,               "QUIET",   "QUIET",   NULL, NULL, NULL, "Disable verbose messages" },
+
+    { MTAB_XTD | MTAB_VDV, 0, "IOBASE", "IOBASE", &set_iobase, &show_iobase, NULL, "Sets MITS ACR base I/O address" },
+
+    { MTAB_XTD | MTAB_VUN, 0, NULL, "REWIND", &acr_rewind, NULL, NULL, "Rewind cassette" },
+
+    { 0 }
+};
+
+/* Debug Flags */
+static DEBTAB acr_dt[] = {
+    { NULL, 0 }
+};
+
+DEVICE acr_dev = {
+    DEVICE_NAME, &acr_unit, acr_reg, acr_mod,
+    1, ADDRRADIX, ADDRWIDTH, 1, DATARADIX, DATAWIDTH,
+    NULL, NULL, &acr_reset, NULL,
+    &acr_attach, &acr_detach, &acr_res,
+    (DEV_DISABLE | DEV_DIS), 0,
+    acr_dt, NULL, NULL, &acr_show_help, &acr_attach_help, NULL, &acr_description
+};
+
+static t_stat acr_reset(DEVICE *dptr) {
+    if (dptr->flags & DEV_DIS) {    /* Disable Device */
+        s100_bus_remio(acr_res.io_base, acr_res.io_size, &acr_io);
+
+        poc = TRUE;
+
+        return SCPE_OK;
+    }
+
+    if (poc) {
+        s100_bus_addio(acr_res.io_base, acr_res.io_size, &acr_io, DEVICE_NAME);
+
+        poc = FALSE;
+    }
+
+    rdre = ACR_RDRE; /* Receive Data Register Empty */
+
+    return SCPE_OK;
+}
+
+static t_stat acr_attach(UNIT *uptr, const char *cptr)
+{
+    t_stat r;
+
+    rdre = ACR_RDRE;
+
+    if ((r = attach_unit(uptr, cptr)) == SCPE_OK) {
+        acr_rdr();
+    }
+
+    return r;
+}
+
+static t_stat acr_detach(UNIT *uptr)
+{
+    return detach_unit(uptr);
+}
+
+static void acr_rdr()
+{
+    t_stat ch;
+
+    if (acr_unit.fileref != NULL) { /* attached to a file? */
+        if (rdre) {                 /* receive data register empty? */
+            ch = getc(acr_unit.fileref);
+
+            if (ch == EOF) {
+                rdre = ACR_RDRE;
+            } else {
+                rdre = 0x00;                 /* indicate character available */
+
+                rdr = ch;                    /* store character in register  */
+            }
+        }
+    }
+}
+
+static int32 acr_io(const int32 addr, const int32 rw, const int32 data)
+{
+    if (addr & 0x01) {
+        return acr_data(addr, rw, data);
+    }
+
+    if (rw == S100_IO_READ) { /* Return status */
+        return rdre;
+    }
+
+    return 0xff;
+}
+
+static int32 acr_data(const int32 addr, const int32 rw, const int32 data)
+{
+    t_stat ch;
+
+    if (rw == S100_IO_READ) {
+        ch = rdr;
+
+        rdre = ACR_RDRE;  /* Receive data register empty */
+
+        acr_rdr();        /* Check for another character */
+
+        return ch;
+    }
+
+    if (acr_unit.fileref != NULL) {  /* attached to a file? */
+        fputc(data, acr_unit.fileref);
+    }
+    else {
+        sim_putchar(data);
+    }
+
+    return 0xff;
+}
+
+static t_stat acr_rewind(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
+{
+    if (acr_unit.fileref != NULL) {
+        rewind(acr_unit.fileref);
+
+        if (acr_unit.flags & UNIT_ACR_VERBOSE) {
+            sim_printf("TAPE is rewound\n");
+        }
+    }
+    else {
+        sim_printf("No file attached to %s device.\n", DEVICE_NAME);
+    }
+
+    return SCPE_OK;
+}
+
+static t_stat acr_show_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr)
+{
+    fprintf(st, "\n88-ACR (%s)\n", DEVICE_NAME);
+
+    fprint_set_help(st, dptr);
+    fprint_show_help(st, dptr);
+    fprint_reg_help(st, dptr);
+
+    return SCPE_OK;
+}
+
+static t_stat acr_attach_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr)
+{
+    fprintf(st, "\n88-ACR (%s)\n\n", DEVICE_NAME);
+
+    fprintf(st, "The %s device simulates the MITS ACR Audio Cassette Interface\n", DEVICE_NAME);
+    fprintf(st, "and cassette tape recorder.\n");
+
+    fprintf(st, "\nATTACH %s <filename>\n\n", DEVICE_NAME);
+    fprintf(st, "    Inserts a tape into the cassette recorder. Files attached to\n");
+    fprintf(st, "    the %s device are binary files that contain the contants of\n", DEVICE_NAME);
+    fprintf(st, "    the data stored on the tape.\n");
+
+    fprintf(st, "\nDETACH %s\n\n", DEVICE_NAME);
+    fprintf(st, "    Removes a tape from the cassette recorder.\n\n");
+
+    fprintf(st, "\nSHOW %s TAPE\n\n", DEVICE_NAME);
+    fprintf(st, "    Shows the current status of the %s device.\n", DEVICE_NAME);
+
+    fprintf(st, "\nExample:\n\n");
+    fprintf(st, "SET %s ENA\n", DEVICE_NAME);
+    fprintf(st, "ATTACH %s BASIC Ver 1-0.tap\n", DEVICE_NAME);
+    fprintf(st, "HEXLOAD LOAD10.HEX\n");
+    fprintf(st, "SET SIO ENA\n");
+    fprintf(st, "SET SIO BOARD=SIO\n");
+    fprintf(st, "SET SIO CONSOLE\n");
+    fprintf(st, "BREAK -M 117F\n");
+    fprintf(st, "G 1800\n");
+    fprintf(st, "G 0\n\n");
+    fprintf(st, "This example loads ALTAIR BASIC 1.0 from tape using the %s device.\n", DEVICE_NAME);
+    fprintf(st, "The files are available from:\n\n");
+    fprintf(st, "https://deramp.com/downloads/altair/software/papertape_cassette/\n");
+
+    return SCPE_OK;
+}
+
diff --git a/Altair8800/mits_acr.h b/Altair8800/mits_acr.h
new file mode 100644
index 00000000..19c230c3
--- /dev/null
+++ b/Altair8800/mits_acr.h
@@ -0,0 +1,42 @@
+/* mits_acr.h
+
+   Copyright (c) 2025 Patrick A. Linstruth
+
+   Permission is hereby granted, free of charge, to any person obtaining a
+   copy of this software and associated documentation files (the "Software"),
+   to deal in the Software without restriction, including without limitation
+   the rights to use, copy, modify, merge, publish, distribute, sublicense,
+   and/or sell copies of the Software, and to permit persons to whom the
+   Software is furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+   PETER SCHORN BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+   IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+   Except as contained in this notice, the name of Patrick Linstruth shall not
+   be used in advertising or otherwise to promote the sale, use or other dealings
+   in this Software without prior written authorization from Patrick Linstruth.
+
+   History:
+   12/27/25 Initial version
+
+*/
+
+#ifndef MITS_ACR_H_
+#define MITS_ACR_H_
+
+#define UNIT_ACR_V_VERBOSE      (UNIT_V_UF+0)
+#define UNIT_ACR_VERBOSE        (1 << UNIT_ACR_V_VERBOSE)
+
+#define ACR_IOBASE      0x06
+#define ACR_IOSIZE      2
+
+#define ACR_RDRE        0x01
+
+#endif
diff --git a/Altair8800/mits_dsk.c b/Altair8800/mits_dsk.c
index cb07b689..5320696d 100644
--- a/Altair8800/mits_dsk.c
+++ b/Altair8800/mits_dsk.c
@@ -137,7 +137,7 @@ static int32 mdsk12(const int32 port, const int32 io, const int32 data);
 
 static t_stat mdsk_boot(int32 unitno, DEVICE *dptr);
 static t_stat mdsk_reset(DEVICE *dptr);
-static t_stat mdsk_attach(UNIT *uptr, CONST char *cptr);
+static t_stat mdsk_attach(UNIT *uptr, const char *cptr);
 static t_stat mdsk_show_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
 static const char* mdsk_description(DEVICE *dptr);
 
@@ -305,7 +305,7 @@ static t_stat mdsk_reset(DEVICE *dptr)
 }
 /* mdsk_attach - determine type of drive attached based on disk image size */
 
-static t_stat mdsk_attach(UNIT *uptr, CONST char *cptr)
+static t_stat mdsk_attach(UNIT *uptr, const char *cptr)
 {
     int32 thisUnitIndex;
     int32 imageSize;
diff --git a/Altair8800/s100_bram.c b/Altair8800/s100_bram.c
index 2388b1de..6a389d31 100644
--- a/Altair8800/s100_bram.c
+++ b/Altair8800/s100_bram.c
@@ -37,14 +37,14 @@ static t_stat bram_ex                (t_value *vptr, t_addr addr, UNIT *uptr, in
 static int32 bram_io                 (const int32 addr, const int32 rw, const int32 data);
 static int32 bram_memio              (const int32 addr, const int32 rw, const int32 data);
 static t_stat bram_set_banks         (int32 banks);
-static t_stat bram_clear_command     (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat bram_enable_command    (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat bram_randomize_command (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat bram_banks_command     (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
+static t_stat bram_clear_command     (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat bram_enable_command    (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat bram_randomize_command (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat bram_banks_command     (UNIT *uptr, int32 value, const char *cptr, void *desc);
 static void bram_addio               (int32 type);
 static void bram_remio               (int32 type);
 static t_stat bram_set_type          (int32 type);
-static t_stat bram_type_command      (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
+static t_stat bram_type_command      (UNIT *uptr, int32 value, const char *cptr, void *desc);
 static void bram_clear               (void);
 static void bram_randomize           (void);
 static t_stat bram_show_help         (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
@@ -363,7 +363,7 @@ static t_stat bram_set_type(int32 type)
     return SCPE_OK;
 }
 
-static t_stat bram_type_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat bram_type_command(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     return bram_set_type(value);
 }
@@ -385,7 +385,7 @@ static t_stat bram_set_banks(int32 banks) {
     return SCPE_OK;
 }
 
-static t_stat bram_banks_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc) {
+static t_stat bram_banks_command(UNIT *uptr, int32 value, const char *cptr, void *desc) {
     int32 result, banks;
 
     if (cptr == NULL) {
@@ -402,7 +402,7 @@ static t_stat bram_banks_command(UNIT *uptr, int32 value, CONST char *cptr, void
     return SCPE_ARG | SCPE_NOMESSAGE;
 }
 
-static t_stat bram_enable_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc) {
+static t_stat bram_enable_command(UNIT *uptr, int32 value, const char *cptr, void *desc) {
     int32 size;
     t_addr start, end;
 
@@ -437,14 +437,14 @@ static t_stat bram_enable_command(UNIT *uptr, int32 value, CONST char *cptr, voi
     return SCPE_OK;
 }
 
-static t_stat bram_clear_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat bram_clear_command(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     bram_clear();
 
     return SCPE_OK;
 }
 
-static t_stat bram_randomize_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat bram_randomize_command(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     bram_randomize();
 
diff --git a/Altair8800/s100_bus.c b/Altair8800/s100_bus.c
index cdbcd1a3..9d40ad67 100644
--- a/Altair8800/s100_bus.c
+++ b/Altair8800/s100_bus.c
@@ -23,6 +23,9 @@
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from Patrick Linstruth.
 
+   History:
+   07-Nov-2025   PAL   Initial version
+
 */
 
 #include "sim_defs.h"
@@ -33,12 +36,12 @@
 static t_stat bus_reset               (DEVICE *dptr);
 static t_stat bus_dep                 (t_value val, t_addr addr, UNIT *uptr, int32 sw);
 static t_stat bus_ex                  (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw);
-static t_stat bus_cmd_memory          (int32 flag, CONST char *cptr);
-static t_stat bus_show_config         (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
-static t_stat bus_show_console        (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+static t_stat bus_cmd_memory          (int32 flag, const char *cptr);
+static t_stat bus_show_config         (FILE *st, UNIT *uptr, int32 val, const void *desc);
+static t_stat bus_show_console        (FILE *st, UNIT *uptr, int32 val, const void *desc);
 static t_stat bus_show_help           (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
-static t_stat bus_hexload_command     (int32 flag, CONST char *cptr);
-static t_stat bus_hexsave_command     (int32 flag, CONST char *cptr);
+static t_stat bus_hexload_command     (int32 flag, const char *cptr);
+static t_stat bus_hexsave_command     (int32 flag, const char *cptr);
 static t_stat hexload                 (const char *filename, t_addr bias);
 static t_stat hexsave                 (FILE *outFile, t_addr start, t_addr end);
 
@@ -63,12 +66,12 @@ uint8 dataBus[MAX_INT_VECTORS];  /* Data bus value          */
 IDEV idev_in[MAXPAGE];
 IDEV idev_out[MAXPAGE];
 
-int32 nulldev(CONST int32 addr, CONST int32 io, CONST int32 data) { return 0xff; }
+int32 nulldev(const int32 addr, const int32 io, const int32 data) { return 0xff; }
 
 /* Which UNIT is the CONSOLE */
 UNIT *bus_console = NULL;
 
-static CONST char* bus_description(DEVICE *dptr) {
+static const char* bus_description(DEVICE *dptr) {
     return "S100 Bus";
 }
 
@@ -162,9 +165,9 @@ static t_stat bus_dep(t_value val, t_addr addr, UNIT *uptr, int32 sw)
     return SCPE_OK;
 }
 
-static t_stat bus_show_config(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat bus_show_config(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
-    CONST char *last = NULL;
+    const char *last = NULL;
     int i, spage, epage;
 
     /* show memory */
@@ -205,7 +208,7 @@ static t_stat bus_show_config(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
     return SCPE_OK;
 }
 
-static t_stat bus_show_console(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat bus_show_console(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     /* show current CONSOLE unit */
     fprintf(st, "CONSOLE Unit: %s\n", (bus_console == NULL) ? "NONE" : sim_uname(bus_console));
@@ -225,7 +228,7 @@ void s100_bus_get_idev(int32 port, IDEV *idev_in, IDEV *idev_out)
     }
 }
 
-t_stat s100_bus_addio(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32), CONST char *name)
+t_stat s100_bus_addio(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32), const char *name)
 {
     s100_bus_addio_in(port, size, routine, name);
     s100_bus_addio_out(port, size, routine, name);
@@ -233,7 +236,7 @@ t_stat s100_bus_addio(int32 port, int32 size, int32 (*routine)(CONST int32, CONS
     return SCPE_OK;
 }
 
-t_stat s100_bus_addio_in(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32), CONST char *name)
+t_stat s100_bus_addio_in(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32), const char *name)
 {
     int i;
 
@@ -249,7 +252,7 @@ t_stat s100_bus_addio_in(int32 port, int32 size, int32 (*routine)(CONST int32, C
     return SCPE_OK;
 }
 
-t_stat s100_bus_addio_out(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32), CONST char *name)
+t_stat s100_bus_addio_out(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32), const char *name)
 {
     int i;
 
@@ -266,7 +269,7 @@ t_stat s100_bus_addio_out(int32 port, int32 size, int32 (*routine)(CONST int32,
 }
 
 
-t_stat s100_bus_remio(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32))
+t_stat s100_bus_remio(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32))
 {
     s100_bus_remio_in(port, size, routine);
     s100_bus_remio_out(port, size, routine);
@@ -274,7 +277,7 @@ t_stat s100_bus_remio(int32 port, int32 size, int32 (*routine)(CONST int32, CONS
     return SCPE_OK;
 }
 
-t_stat s100_bus_remio_in(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32))
+t_stat s100_bus_remio_in(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32))
 {
     int i;
 
@@ -292,7 +295,7 @@ t_stat s100_bus_remio_in(int32 port, int32 size, int32 (*routine)(CONST int32, C
     return SCPE_OK;
 }
 
-t_stat s100_bus_remio_out(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32))
+t_stat s100_bus_remio_out(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32))
 {
     int i;
 
@@ -323,7 +326,7 @@ void s100_bus_get_mdev(int32 addr, MDEV *mdev)
 }
 
 t_stat s100_bus_addmem(int32 baseaddr, uint32 size, 
-    int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data), CONST char *name)
+    int32 (*routine)(const int32 addr, const int32 rw, const int32 data), const char *name)
 {
     int32 page;
     uint32 i;
@@ -346,7 +349,7 @@ t_stat s100_bus_addmem(int32 baseaddr, uint32 size,
     return SCPE_OK;
 }
 
-t_stat s100_bus_setmem_dflt(int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data), CONST char *name)
+t_stat s100_bus_setmem_dflt(int32 (*routine)(const int32 addr, const int32 rw, const int32 data), const char *name)
 {
     mdev_dflt.routine = routine;
     mdev_dflt.name = name;
@@ -355,7 +358,7 @@ t_stat s100_bus_setmem_dflt(int32 (*routine)(CONST int32 addr, CONST int32 rw, C
 }
 
 t_stat s100_bus_remmem(int32 baseaddr, uint32 size, 
-    int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data))
+    int32 (*routine)(const int32 addr, const int32 rw, const int32 data))
 {
     int32 page;
     uint32 i;
@@ -372,7 +375,7 @@ t_stat s100_bus_remmem(int32 baseaddr, uint32 size,
     return SCPE_OK;
 }
 
-t_stat s100_bus_remmem_dflt(int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data))
+t_stat s100_bus_remmem_dflt(int32 (*routine)(const int32 addr, const int32 rw, const int32 data))
 {
     if (mdev_dflt.routine == routine) {
         mdev_dflt.routine = &nulldev;
@@ -474,7 +477,7 @@ void s100_bus_clr_nmi()
     nmiInterrupt = FALSE;
 }
 
-static t_stat bus_cmd_memory(int32 flag, CONST char *cptr)
+static t_stat bus_cmd_memory(int32 flag, const char *cptr)
 {
     char abuf[16];
     t_addr lo, hi, last;
@@ -536,12 +539,12 @@ static t_stat bus_cmd_memory(int32 flag, CONST char *cptr)
     ALTAIRROM/NOALTAIRROM settings are ignored.
 */
 
-t_stat sim_load(FILE *fileref, CONST char *cptr, CONST char *fnam, int flag)
+t_stat sim_load(FILE *fileref, const char *cptr, const char *fnam, int flag)
 {
     int32 i;
     uint32 addr, cnt = 0, org;
     t_addr j, lo, hi;
-    CONST char *result;
+    const char *result;
     char gbuf[CBUFSIZE];
 
     if (flag) { /* dump ram to file */
@@ -593,7 +596,7 @@ t_stat sim_load(FILE *fileref, CONST char *cptr, CONST char *fnam, int flag)
     return SCPE_OK;
 }
 
-static t_stat bus_hexload_command(int32 flag, CONST char *cptr)
+static t_stat bus_hexload_command(int32 flag, const char *cptr)
 {
     char filename[4*CBUFSIZE];
     t_addr lo = 0, hi = 0;
@@ -618,7 +621,7 @@ static t_stat bus_hexload_command(int32 flag, CONST char *cptr)
     return SCPE_OK;
 }
 
-static t_stat bus_hexsave_command(int32 flag, CONST char *cptr)
+static t_stat bus_hexsave_command(int32 flag, const char *cptr)
 {
     char filename[4*CBUFSIZE];
     FILE *sfile;
@@ -810,39 +813,46 @@ static t_stat hexsave(FILE *outFile, t_addr start, t_addr end)
  */
 
 /* Set Memory Base Address routine */
-t_stat set_membase(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
+t_stat set_membase(UNIT *uptr, int32 val, const char *cptr, void *desc)
 {
     DEVICE *dptr;
     RES *res;
     uint32 newba;
     t_stat r;
 
-    if (cptr == NULL)
+    if (cptr == NULL) {
         return SCPE_ARG;
+    }
 
-    if (uptr == NULL)
+    if (uptr == NULL) {
         return SCPE_IERR;
+    }
 
-    if ((dptr = find_dev_from_unit(uptr)) == NULL)
+    if ((dptr = find_dev_from_unit(uptr)) == NULL) {
         return SCPE_IERR;
+    }
 
     res = (RES *) dptr->ctxt;
 
-    if (res == NULL)
+    if (res == NULL) {
         return SCPE_IERR;
+    }
 
     newba = get_uint (cptr, 16, 0xFFFF, &r);
 
-    if (r != SCPE_OK)
+    if (r != SCPE_OK) {
         return r;
+    }
 
-    if ((newba > 0xFFFF) || (newba % res->mem_size))
+    if ((newba > 0xFFFF) || (newba % res->mem_size)) {
         return SCPE_ARG;
+    }
 
     if (dptr->flags & DEV_DIS) {
         sim_printf("device not enabled yet.\n");
         res->mem_base = newba & ~(res->mem_size-1);
-    } else {
+    }
+    else {
         dptr->flags |= DEV_DIS;
         dptr->reset(dptr);
         res->mem_base = newba & ~(res->mem_size-1);
@@ -854,21 +864,24 @@ t_stat set_membase(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 }
 
 /* Show Base Address routine */
-t_stat show_membase(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+t_stat show_membase(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     DEVICE *dptr;
     RES *res;
 
-    if (uptr == NULL)
+    if (uptr == NULL) {
         return SCPE_IERR;
+    }
 
-    if ((dptr = find_dev_from_unit(uptr)) == NULL)
+    if ((dptr = find_dev_from_unit(uptr)) == NULL) {
         return SCPE_IERR;
+    }
 
     res = (RES *) dptr->ctxt;
 
-    if (res == NULL)
+    if (res == NULL) {
         return SCPE_IERR;
+    }
 
     fprintf(st, "MEM=0x%04X-0x%04X", res->mem_base, res->mem_base + res->mem_size-1);
 
@@ -876,34 +889,40 @@ t_stat show_membase(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 }
 
 /* Set Memory Base Address routine */
-t_stat set_iobase(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
+t_stat set_iobase(UNIT *uptr, int32 val, const char *cptr, void *desc)
 {
     DEVICE *dptr;
     RES *res;
     uint32 newba;
     t_stat r;
 
-    if (cptr == NULL)
+    if (cptr == NULL) {
         return SCPE_ARG;
+    }
 
-    if (uptr == NULL)
+    if (uptr == NULL) {
         return SCPE_IERR;
+    }
 
-    if ((dptr = find_dev_from_unit(uptr)) == NULL)
+    if ((dptr = find_dev_from_unit(uptr)) == NULL) {
         return SCPE_IERR;
+    }
 
     res = (RES *) dptr->ctxt;
 
-    if (res == NULL)
+    if (res == NULL) {
         return SCPE_IERR;
+    }
 
     newba = get_uint (cptr, 16, 0xFF, &r);
 
-    if (r != SCPE_OK)
+    if (r != SCPE_OK) {
         return r;
+    }
 
-    if ((newba > 0xFF) || (newba % res->io_size))
+    if ((newba > 0xFF) || (newba % res->io_size)) {
         return SCPE_ARG;
+    }
 
     if (dptr->flags & DEV_DIS) {
         sim_printf("device not enabled yet.\n");
@@ -920,21 +939,24 @@ t_stat set_iobase(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 }
 
 /* Show I/O Base Address routine */
-t_stat show_iobase(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+t_stat show_iobase(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     DEVICE *dptr;
     RES *res;
 
-    if (uptr == NULL)
+    if (uptr == NULL) {
         return SCPE_IERR;
+    }
 
-    if ((dptr = find_dev_from_unit(uptr)) == NULL)
+    if ((dptr = find_dev_from_unit(uptr)) == NULL) {
         return SCPE_IERR;
+    }
 
     res = (RES *) dptr->ctxt;
 
-    if (res == NULL)
+    if (res == NULL) {
         return SCPE_IERR;
+    }
 
     fprintf(st, "I/O=0x%02X-0x%02X", res->io_base, res->io_base + res->io_size-1);
 
diff --git a/Altair8800/s100_bus.h b/Altair8800/s100_bus.h
index 5165a975..f99c6025 100644
--- a/Altair8800/s100_bus.h
+++ b/Altair8800/s100_bus.h
@@ -91,31 +91,31 @@ typedef struct {
 
 /* data structure for IN/OUT instructions */
 typedef struct idev {
-    int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data);
-    CONST char *name;
+    int32 (*routine)(const int32 addr, const int32 rw, const int32 data);
+    const char *name;
 } IDEV;
 
 typedef struct { /* Structure to describe memory device address space */
-    int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data);
-    CONST char *name; /* name of handler routine */
+    int32 (*routine)(const int32 addr, const int32 rw, const int32 data);
+    const char *name; /* name of handler routine */
 } MDEV;
 
-extern t_stat s100_bus_addio(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32), CONST char* name);
-extern t_stat s100_bus_addio_in(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32), CONST char* name);
-extern t_stat s100_bus_addio_out(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32), CONST char* name);
-extern t_stat s100_bus_remio(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32));
-extern t_stat s100_bus_remio_in(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32));
-extern t_stat s100_bus_remio_out(int32 port, int32 size, int32 (*routine)(CONST int32, CONST int32, CONST int32));
+extern t_stat s100_bus_addio(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32), const char* name);
+extern t_stat s100_bus_addio_in(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32), const char* name);
+extern t_stat s100_bus_addio_out(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32), const char* name);
+extern t_stat s100_bus_remio(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32));
+extern t_stat s100_bus_remio_in(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32));
+extern t_stat s100_bus_remio_out(int32 port, int32 size, int32 (*routine)(const int32, const int32, const int32));
 extern t_stat s100_bus_addmem(int32 baseaddr, uint32 size, 
-    int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data), CONST char *name);
+    int32 (*routine)(const int32 addr, const int32 rw, const int32 data), const char *name);
 extern t_stat s100_bus_remmem(int32 baseaddr, uint32 size, 
-    int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data));
-extern t_stat s100_bus_setmem_dflt(int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data), CONST char *name);
-extern t_stat s100_bus_remmem_dflt(int32 (*routine)(CONST int32 addr, CONST int32 rw, CONST int32 data));
+    int32 (*routine)(const int32 addr, const int32 rw, const int32 data));
+extern t_stat s100_bus_setmem_dflt(int32 (*routine)(const int32 addr, const int32 rw, const int32 data), const char *name);
+extern t_stat s100_bus_remmem_dflt(int32 (*routine)(const int32 addr, const int32 rw, const int32 data));
 
 extern void s100_bus_get_idev(int32 port, IDEV *idev_in, IDEV *idev_out);
 extern void s100_bus_get_mdev(int32 addr, MDEV *mdev);
-extern int32 nulldev(CONST int32 addr, CONST int32 io, CONST int32 data);
+extern int32 nulldev(const int32 addr, const int32 io, const int32 data);
 
 extern uint32 s100_bus_set_addr(uint32 pc);
 extern uint32 s100_bus_get_addr(void);
@@ -147,10 +147,10 @@ extern void s100_bus_clr_nmi(void);
 
 #define sim_map_resource(a,b,c,d,e,f) s100_map_resource(a,b,c,d,e,f)
 
-extern t_stat set_iobase(UNIT *uptr, int32 val, CONST char *cptr, void *desc);
-extern t_stat show_iobase(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
-extern t_stat set_membase(UNIT *uptr, int32 val, CONST char *cptr, void *desc);
-extern t_stat show_membase(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+extern t_stat set_iobase(UNIT *uptr, int32 val, const char *cptr, void *desc);
+extern t_stat show_iobase(FILE *st, UNIT *uptr, int32 val, const void *desc);
+extern t_stat set_membase(UNIT *uptr, int32 val, const char *cptr, void *desc);
+extern t_stat show_membase(FILE *st, UNIT *uptr, int32 val, const void *desc);
 extern void cpu_raise_interrupt(uint32 irq);
 
 #endif
diff --git a/Altair8800/s100_cpu.c b/Altair8800/s100_cpu.c
index 58f1706c..7cffa6e8 100644
--- a/Altair8800/s100_cpu.c
+++ b/Altair8800/s100_cpu.c
@@ -46,14 +46,14 @@ static char *cpu_chipname[] = {
 };
 
 static t_stat (*cpu_instr)(void) = NULL;
-static t_stat (*cpu_parse_sym)(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw) = NULL;
+static t_stat (*cpu_parse_sym)(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw) = NULL;
 static int32  (*cpu_dasm)(char *S, const uint32 *val, const int32 addr) = NULL;
 
 static t_stat cpu_reset(DEVICE *dptr);
 static void cpu_set_instr(t_stat (*routine)(void));
 static void cpu_set_pc(REG *reg);
 static void cpu_set_pc_value(t_value (*routine)(void));
-static void cpu_set_parse_sym(t_stat (*routine)(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw));
+static void cpu_set_parse_sym(t_stat (*routine)(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw));
 static void cpu_set_dasm(int32 (*routine)(char *S, const uint32 *val, const int32 addr));
 static void cpu_set_is_subroutine_call(t_bool (*routine)(t_addr **ret_addrs));
 
@@ -190,7 +190,7 @@ static void cpu_set_pc_value(t_value (*routine)(void))
     sim_vm_pc_value = routine;
 }
 
-static void cpu_set_parse_sym(t_stat (*routine)(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw))
+static void cpu_set_parse_sym(t_stat (*routine)(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw))
 {
     cpu_parse_sym = routine;
 }
@@ -227,7 +227,7 @@ t_stat fprint_sym(FILE *of, t_addr addr, t_value *val, UNIT *uptr, int32 sw)
     return 1 - r;
 }
 
-t_stat parse_sym(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
+t_stat parse_sym(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
 {
     while (isspace(*cptr)) {
         cptr++; /* absorb spaces */
diff --git a/Altair8800/s100_cpu.h b/Altair8800/s100_cpu.h
index a526474e..bbc5b60b 100644
--- a/Altair8800/s100_cpu.h
+++ b/Altair8800/s100_cpu.h
@@ -49,7 +49,7 @@ typedef struct {
     ChipType *chiptype;
     t_stat   (*instr)(void);
     t_value  (*pc_val)(void);
-    t_stat   (*parse_sym)(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw);
+    t_stat   (*parse_sym)(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw);
     int32    (*dasm)(char *S, const uint32 *val, const int32 addr);
     t_bool   (*isc)(t_addr **ret_addrs);
     t_stat   (*help)(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
diff --git a/Altair8800/s100_ram.c b/Altair8800/s100_ram.c
index 0246f86b..31026d64 100644
--- a/Altair8800/s100_ram.c
+++ b/Altair8800/s100_ram.c
@@ -36,13 +36,13 @@ static t_stat ram_reset             (DEVICE *dptr);
 static t_stat ram_dep               (t_value val, t_addr addr, UNIT *uptr, int32 sw);
 static t_stat ram_ex                (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw);
 static int32 ram_memio              (const int32 addr, const int32 rw, const int32 data);
-static t_stat ram_default_ena       (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat ram_default_dis       (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
+static t_stat ram_default_ena       (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat ram_default_dis       (UNIT *uptr, int32 value, const char *cptr, void *desc);
 static t_stat ram_set_memsize       (int32 value);
-static t_stat ram_clear_command     (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat ram_enable_command    (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat ram_randomize_command (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat ram_size_command      (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
+static t_stat ram_clear_command     (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat ram_enable_command    (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat ram_randomize_command (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat ram_size_command      (UNIT *uptr, int32 value, const char *cptr, void *desc);
 static void ram_clear               (void);
 static void ram_randomize           (void);
 static t_stat ram_show_help         (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
@@ -185,14 +185,14 @@ static uint32 GetBYTE(register uint32 Addr)
     return M[Addr & ADDRMASK] & DATAMASK; /* RAM */
 }
 
-static t_stat ram_default_ena(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat ram_default_ena(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     s100_bus_setmem_dflt(&ram_memio, "RAM"); /* Set RAM as default memory device */
 
     return SCPE_OK;
 }
 
-static t_stat ram_default_dis(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat ram_default_dis(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     s100_bus_remmem_dflt(&ram_memio);       /* Remove RAM as default memory device */
 
@@ -246,7 +246,7 @@ static void ram_randomize()
     }
 }
 
-static t_stat ram_size_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc) {
+static t_stat ram_size_command(UNIT *uptr, int32 value, const char *cptr, void *desc) {
     int32 size, result;
 
     if (cptr == NULL) {
@@ -263,7 +263,7 @@ static t_stat ram_size_command(UNIT *uptr, int32 value, CONST char *cptr, void *
     return SCPE_ARG | SCPE_NOMESSAGE;
 }
 
-static t_stat ram_enable_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc) {
+static t_stat ram_enable_command(UNIT *uptr, int32 value, const char *cptr, void *desc) {
     int32 size;
     t_addr start, end;
 
@@ -298,14 +298,14 @@ static t_stat ram_enable_command(UNIT *uptr, int32 value, CONST char *cptr, void
     return SCPE_OK;
 }
 
-static t_stat ram_clear_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat ram_clear_command(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     ram_clear();
 
     return SCPE_OK;
 }
 
-static t_stat ram_randomize_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat ram_randomize_command(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     ram_randomize();
 
diff --git a/Altair8800/s100_rom.c b/Altair8800/s100_rom.c
index 31d5f369..dfbd4b61 100644
--- a/Altair8800/s100_rom.c
+++ b/Altair8800/s100_rom.c
@@ -44,12 +44,12 @@ static const char* rom_description  (DEVICE *dptr);
 static uint32 GetBYTE(register uint32 Addr);
 
 static t_stat rom_enadis(int32 value, int32 ena);
-static t_stat rom_ena(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat rom_dis_dbl(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat rom_dis_hdsk(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat rom_dis_altmon(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat rom_dis_turmon(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat rom_show_list(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+static t_stat rom_ena(UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat rom_dis_dbl(UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat rom_dis_hdsk(UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat rom_dis_altmon(UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat rom_dis_turmon(UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat rom_show_list(FILE *st, UNIT *uptr, int32 val, const void *desc);
 static t_stat rom_show_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
 
 static int32 M[MAXBANKSIZE];
@@ -193,32 +193,32 @@ static t_stat rom_enadis(int32 value, int32 ena)
     return SCPE_OK;
 }
 
-static t_stat rom_ena(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat rom_ena(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     return rom_enadis(value, TRUE);
 }
 
-static t_stat rom_dis_dbl(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat rom_dis_dbl(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     return rom_enadis(UNIT_ROM_DBL, FALSE);
 }
 
-static t_stat rom_dis_hdsk(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat rom_dis_hdsk(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     return rom_enadis(UNIT_ROM_HDSK, FALSE);
 }
 
-static t_stat rom_dis_turmon(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat rom_dis_turmon(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     return rom_enadis(UNIT_ROM_TURMON, FALSE);
 }
 
-static t_stat rom_dis_altmon(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat rom_dis_altmon(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     return rom_enadis(UNIT_ROM_ALTMON, FALSE);
 }
 
-static t_stat rom_show_list(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat rom_show_list(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     ROM *r = rom_table;
 
diff --git a/Altair8800/s100_sio.c b/Altair8800/s100_sio.c
index a4985f2b..fd9ec666 100644
--- a/Altair8800/s100_sio.c
+++ b/Altair8800/s100_sio.c
@@ -24,7 +24,8 @@
    in this Software without prior written authorization from Patrick Linstruth.
 
    History:
-   07-Nov-2025 Initial version
+   07-Nov-2025   PAL   Initial version
+   23-Nov-2025   PAL   Do not add IO to the BUS if device is disabled
 
 */
 
@@ -73,15 +74,17 @@ static int32 sio_rdre;   /* Receive Data Register Empty Flag */
 static int32 sio_tdre;   /* Transmit Buffer Full Empty       */
 
 static t_stat sio_reset(DEVICE *dptr);
+static t_stat sio_addio(UNIT *uptr);
+static t_stat sio_remio();
 static int32 sio_io(const int32 addr, const int32 rw, const int32 data);
 static int32 sio_io_in(const int32 addr);
 static void sio_io_out(const int32 addr, int32 data);
-static t_stat sio_set_board(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat sio_set_type (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat sio_set_val(UNIT *uptr, int32 value, CONST char *cptr, void *desc);
+static t_stat sio_set_board(UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat sio_set_type (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat sio_set_val(UNIT *uptr, int32 value, const char *cptr, void *desc);
 static t_stat sio_set_console(UNIT *uptr, int32 value, const char *cptr, void *desc);
-static t_stat sio_show_config(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
-static t_stat sio_show_list(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+static t_stat sio_show_config(FILE *st, UNIT *uptr, int32 val, const void *desc);
+static t_stat sio_show_list(FILE *st, UNIT *uptr, int32 val, const void *desc);
 static t_stat sio_show_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
 
 static const char* sio_description(DEVICE *dptr) {
@@ -161,8 +164,9 @@ static t_stat sio_reset(DEVICE *dptr)
 {
     if (dptr->flags & DEV_DIS) {    /* Disable Device */
         if (sio_type != SIO_TYPE_NONE) {
-            s100_bus_remio(sio.stat, 1, &sio_io);
-            s100_bus_remio(sio.data, 1, &sio_io);
+            sio_remio();
+
+            sio_type = SIO_TYPE_NONE;
 
             s100_bus_noconsole(&dptr->units[0]);
         }
@@ -188,11 +192,44 @@ static t_stat sio_reset(DEVICE *dptr)
     sio_rdre = TRUE;
     sio_tdre = TRUE;
 
+    sio_addio(&dptr->units[0]);
+
     sim_debug(STATUS_MSG, dptr, "reset adapter.\n");
 
     return SCPE_OK;
 }
 
+static t_stat sio_remio()
+{
+    s100_bus_remio(sio.base + sio.stat, 1, &sio_io);
+    s100_bus_remio(sio.base + sio.data, 1, &sio_io);
+
+    return SCPE_OK;
+}
+
+static t_stat sio_addio(UNIT *uptr)
+{
+    DEVICE *dptr;
+
+    if (uptr == NULL) {
+        return SCPE_IERR;
+    }
+
+    if ((dptr = find_dev_from_unit(uptr)) == NULL) {
+        return SCPE_IERR;
+    }
+
+    if (dptr->flags & DEV_DIS) {
+        sim_printf("%s device not enabled yet.\n", dptr->name);
+    }
+    else if (sio_type != SIO_TYPE_NONE) {
+        s100_bus_addio(sio.base + sio.stat, 1, &sio_io, SIO_SNAME"S");
+        s100_bus_addio(sio.base + sio.data, 1, &sio_io, SIO_SNAME"D");
+    }
+
+    return SCPE_OK;
+}
+
 static int32 sio_io(const int32 addr, const int32 rw, const int32 data)
 {
     int32 c;
@@ -242,7 +279,7 @@ static void sio_io_out(const int32 addr, int32 data)
     }
 }
 
-static t_stat sio_set_type(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat sio_set_type(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     int32 result, base;
 
@@ -251,8 +288,7 @@ static t_stat sio_set_type(UNIT *uptr, int32 value, CONST char *cptr, void *desc
     }
 
     if (sio_type != SIO_TYPE_NONE) {
-        s100_bus_remio(sio.base + sio.stat, 1, &sio_io);
-        s100_bus_remio(sio.base + sio.data, 1, &sio_io);
+        sio_remio();
     }
 
     sio_type = value;
@@ -277,14 +313,15 @@ static t_stat sio_set_type(UNIT *uptr, int32 value, CONST char *cptr, void *desc
             }
         }
 
-        s100_bus_addio(sio.base + sio.stat, 1, &sio_io, SIO_SNAME"S");
-        s100_bus_addio(sio.base + sio.data, 1, &sio_io, SIO_SNAME"D");
+        if (!(uptr->flags & UNIT_DIS)) {
+            sio_addio(uptr);
+        }
     }
 
     return SCPE_OK;
 }
 
-static t_stat sio_set_board(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat sio_set_board(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     char cbuf[10];
     int i = 0;
@@ -303,7 +340,7 @@ static t_stat sio_set_board(UNIT *uptr, int32 value, CONST char *cptr, void *des
     return SCPE_ARG;
 }
 
-static t_stat sio_set_val(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat sio_set_val(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     uint32 val;
 
@@ -311,6 +348,9 @@ static t_stat sio_set_val(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
         return SCPE_ARG;
     }
 
+    /* Remove current configuration */
+    sio_remio();
+
     val &= DATAMASK;
 
     switch (value) {
@@ -351,12 +391,17 @@ static t_stat sio_set_val(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
     sio.type = SIO_TYPE_CUST;
     sio_type = SIO_TYPE_CUST;
 
+    /* Add new configuration */
+    if (!(uptr->flags & UNIT_DIS)) {
+        sio_addio(uptr);
+    }
+
     return SCPE_OK;
 }
 
 static t_stat sio_set_console(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
-    if (value == UNIT_SIO_CONSOLE) {
+    if (value == UNIT_SIO_CONSOLE && !(uptr->flags & UNIT_DIS)) {
         s100_bus_console(uptr);
     }
     else {
@@ -366,7 +411,7 @@ static t_stat sio_set_console(UNIT *uptr, int32 value, const char *cptr, void *d
     return SCPE_OK;
 }
 
-static t_stat sio_show_config(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat sio_show_config(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     if (sio_type != SIO_TYPE_NONE) {
         sim_printf("SIO Base Address:    %02X\n\n", sio.base);
@@ -388,7 +433,7 @@ static t_stat sio_show_config(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
     return SCPE_OK;
 }
 
-static t_stat sio_show_list(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat sio_show_list(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     int i;
 
diff --git a/Altair8800/s100_z80.c b/Altair8800/s100_z80.c
index 078f850c..5d794827 100644
--- a/Altair8800/s100_z80.c
+++ b/Altair8800/s100_z80.c
@@ -131,11 +131,11 @@ static int32 poc = TRUE; /* Power On Clear */
 #define INCR(val) IR_S = (IR_S & ~0x7f) | ((IR_S + (val)) & 0x7f)
 
 /* function prototypes */
-static t_stat z80_set_chiptype      (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
-static t_stat z80_set_hist          (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
-static t_stat z80_show_hist         (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
-static t_stat z80_show              (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
-static t_stat chip_show             (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+static t_stat z80_set_chiptype      (UNIT *uptr, int32 value, const char *cptr, void *desc);
+static t_stat z80_set_hist          (UNIT *uptr, int32 val, const char *cptr, void *desc);
+static t_stat z80_show_hist         (FILE *st, UNIT *uptr, int32 val, const void *desc);
+static t_stat z80_show              (FILE *st, UNIT *uptr, int32 val, const void *desc);
+static t_stat chip_show             (FILE *st, UNIT *uptr, int32 val, const void *desc);
 static t_stat z80_reset(DEVICE *dptr);
 static const char* z80_description(DEVICE *dptr);
 
@@ -5732,7 +5732,7 @@ t_bool z80_is_pc_a_subroutine_call (t_addr **ret_addrs)
     return FALSE;
 }
 
-static t_stat chip_show(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat chip_show(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     fprintf(st, z80_unit.flags & UNIT_Z80_OPSTOP ? "ITRAP, " : "NOITRAP, ");
     if ((z80_chiptype >= 0) && (z80_chiptype < NUM_CHIP_TYPE)) {
@@ -5742,7 +5742,7 @@ static t_stat chip_show(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
     return SCPE_OK;
 }
 
-static t_stat z80_show(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat z80_show(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     if (z80_unit.flags & UNIT_CPU_VERBOSE) {
         fprintf(st, "VERBOSE");
@@ -5751,7 +5751,7 @@ static t_stat z80_show(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
     return SCPE_OK;
 }
 
-static t_stat z80_set_chiptype(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
+static t_stat z80_set_chiptype(UNIT *uptr, int32 value, const char *cptr, void *desc)
 {
     if (z80_chiptype != value) {
         if (z80_unit.flags & UNIT_CPU_VERBOSE) {
@@ -5764,7 +5764,7 @@ static t_stat z80_set_chiptype(UNIT *uptr, int32 value, CONST char *cptr, void *
     return SCPE_OK;
 }
 
-static t_stat z80_set_hist(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
+static t_stat z80_set_hist(UNIT *uptr, int32 val, const char *cptr, void *desc)
 {
     uint32 i, lnt;
     t_stat r;
@@ -5828,10 +5828,10 @@ static t_stat z80_set_hist(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
     return SCPE_OK;
 }
 
-t_stat z80_show_hist (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+t_stat z80_show_hist (FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     int32 k, di, lnt;
-    CONST char *cptr = (CONST char *) desc;
+    const char *cptr = (const char *) desc;
     t_stat r;
     insthist_t *h;
 
@@ -5910,7 +5910,7 @@ t_value z80_pc_value (void) {
     return (t_value) PCX;
 }
 
-t_stat z80_cmd_reg(int32 flag, CONST char *cptr)
+t_stat z80_cmd_reg(int32 flag, const char *cptr)
 {
     t_value op[INST_MAX_BYTES];
     int i;
@@ -6531,7 +6531,7 @@ static int32 parse_X80(const char *cptr, const int32 addr, uint32 *val, const ch
     return SCPE_ARG;
 }
 
-t_stat z80_parse_sym(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
+t_stat z80_parse_sym(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
 {
     return (parse_X80(cptr, addr, val, z80_chiptype == CHIP_TYPE_Z80 ? MnemonicsZ80 : Mnemonics8080));
 }
diff --git a/Altair8800/s100_z80.h b/Altair8800/s100_z80.h
index a52b3902..ad1ffc9f 100644
--- a/Altair8800/s100_z80.h
+++ b/Altair8800/s100_z80.h
@@ -60,10 +60,10 @@ extern REG *z80_pc_reg;
 
 extern t_stat z80_instr(void);
 extern t_value z80_pc_value(void);
-extern t_stat z80_parse_sym(CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw);
+extern t_stat z80_parse_sym(const char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw);
 extern t_bool z80_is_pc_a_subroutine_call (t_addr **ret_addrs);
 extern int32 z80_dasm(char *S, const uint32 *val, const int32 addr);
-extern t_stat z80_cmd_reg(int32 flag, CONST char *cptr);
+extern t_stat z80_cmd_reg(int32 flag, const char *cptr);
 extern t_bool z80_is_pc_a_subroutine_call(t_addr **ret_addrs);
 extern t_stat z80_show_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
 
diff --git a/Altair8800/sds_sbc200.c b/Altair8800/sds_sbc200.c
index d42dd371..7c98061b 100644
--- a/Altair8800/sds_sbc200.c
+++ b/Altair8800/sds_sbc200.c
@@ -639,7 +639,7 @@ typedef struct {
 static const char* sbc200_description(DEVICE *dptr);
 static t_stat sbc200_svc(UNIT *uptr);
 static t_stat sbc200_reset(DEVICE *dptr);
-static t_stat sbc200_attach(UNIT *uptr, CONST char *cptr);
+static t_stat sbc200_attach(UNIT *uptr, const char *cptr);
 static t_stat sbc200_detach(UNIT *uptr);
 static t_stat sbc200_set_console(UNIT *uptr, int32 value, const char *cptr, void *desc);
 static t_stat sbc200_set_baud(UNIT *uptr, int32 value, const char *cptr, void *desc);
@@ -941,7 +941,7 @@ static t_stat sbc200_svc(UNIT *uptr)
 
 
 /* Attach routine */
-static t_stat sbc200_attach(UNIT *uptr, CONST char *cptr)
+static t_stat sbc200_attach(UNIT *uptr, const char *cptr)
 {
     t_stat r;
 
diff --git a/Altair8800/sds_vfii.c b/Altair8800/sds_vfii.c
index 7e7cbcdd..8af1b64d 100644
--- a/Altair8800/sds_vfii.c
+++ b/Altair8800/sds_vfii.c
@@ -50,7 +50,7 @@ static RES vfii_res = { VFII_IO_BASE, VFII_IO_SIZE, 0x0000, 0x0000 };
 static DSK_INFO dsk_info[VFII_NUM_DRIVES];
 
 static t_stat vfii_reset(DEVICE *vfii_dev);
-static t_stat vfii_attach(UNIT *uptr, CONST char *cptr);
+static t_stat vfii_attach(UNIT *uptr, const char *cptr);
 static t_stat vfii_detach(UNIT *uptr);
 static t_stat vfii_boot(int32 unitno, DEVICE *dptr);
 static int32 vfii_io(const int32 port, const int32 io, const int32 data);
@@ -188,7 +188,7 @@ static t_stat vfii_boot(int32 unitno, DEVICE *dptr)
 }
 
 /* Attach routine */
-static t_stat vfii_attach(UNIT *uptr, CONST char *cptr)
+static t_stat vfii_attach(UNIT *uptr, const char *cptr)
 {
     t_stat r;
     int d;
diff --git a/Altair8800/tarbell_fdc.c b/Altair8800/tarbell_fdc.c
index 4cf8968a..544b071c 100644
--- a/Altair8800/tarbell_fdc.c
+++ b/Altair8800/tarbell_fdc.c
@@ -69,13 +69,13 @@ static uint8 tarbell_prom[TARBELL_PROM_SIZE] = {
 };
 
 static t_stat tarbell_reset(DEVICE *tarbell_dev);
-static t_stat tarbell_attach(UNIT *uptr, CONST char *cptr);
+static t_stat tarbell_attach(UNIT *uptr, const char *cptr);
 static t_stat tarbell_detach(UNIT *uptr);
 static t_stat tarbell_boot(int32 unitno, DEVICE *dptr);
-static t_stat tarbell_set_model(UNIT *uptr, int32 val, CONST char *cptr, void *desc);
-static t_stat tarbell_show_model(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
-static t_stat tarbell_set_prom(UNIT *uptr, int32 val, CONST char *cptr, void *desc);
-static t_stat tarbell_show_prom(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+static t_stat tarbell_set_model(UNIT *uptr, int32 val, const char *cptr, void *desc);
+static t_stat tarbell_show_model(FILE *st, UNIT *uptr, int32 val, const void *desc);
+static t_stat tarbell_set_prom(UNIT *uptr, int32 val, const char *cptr, void *desc);
+static t_stat tarbell_show_prom(FILE *st, UNIT *uptr, int32 val, const void *desc);
 static void tarbell_enable_prom(void);
 static void tarbell_disable_prom(void);
 static int32 tarbell_io(const int32 port, const int32 io, const int32 data);
@@ -216,7 +216,7 @@ static t_stat tarbell_boot(int32 unitno, DEVICE *dptr)
 }
 
 /* Attach routine */
-static t_stat tarbell_attach(UNIT *uptr, CONST char *cptr)
+static t_stat tarbell_attach(UNIT *uptr, const char *cptr)
 {
     t_stat r;
     int d;
@@ -377,7 +377,7 @@ static int32 tarbell_memio(const int32 addr, const int32 rw, const int32 data)
     return 0xff;
 }
 
-static t_stat tarbell_set_model(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
+static t_stat tarbell_set_model(UNIT *uptr, int32 val, const char *cptr, void *desc)
 {
     if (!cptr) return SCPE_IERR;
 
@@ -401,14 +401,14 @@ static t_stat tarbell_set_model(UNIT *uptr, int32 val, CONST char *cptr, void *d
     return SCPE_OK;
 }
 
-static t_stat tarbell_show_model(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat tarbell_show_model(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     fprintf(st, "MODEL=%s", (ddfdc_enabled) ? "2022DD" : "1011SD");
 
     return SCPE_OK;
 }
 
-static t_stat tarbell_set_prom(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
+static t_stat tarbell_set_prom(UNIT *uptr, int32 val, const char *cptr, void *desc)
 {
     if (!cptr) return SCPE_IERR;
     if (!strlen(cptr)) return SCPE_ARG;
@@ -451,7 +451,7 @@ static void tarbell_disable_prom(void)
     prom_enabled = FALSE;
 }
 
-static t_stat tarbell_show_prom(FILE *st, UNIT *uptr, int32 val, CONST void *desc)
+static t_stat tarbell_show_prom(FILE *st, UNIT *uptr, int32 val, const void *desc)
 {
     fprintf(st, "%s (%sactive)", (prom_enabled) ? "PROM" : "NOPROM", (prom_active) ? "" : "in");
 
diff --git a/Visual Studio Projects/Altair8800.vcproj b/Visual Studio Projects/Altair8800.vcproj
index 99815a9e..26da4748 100644
--- a/Visual Studio Projects/Altair8800.vcproj	
+++ b/Visual Studio Projects/Altair8800.vcproj	
@@ -207,6 +207,10 @@
 				RelativePath="..\Altair8800\mits_2sio.c"
 				>
 			</File>
+			<File
+				RelativePath="..\Altair8800\mits_acr.c"
+				>
+			</File>
 			<File
 				RelativePath="..\Altair8800\mits_dsk.c"
 				>
@@ -336,6 +340,10 @@
 				RelativePath="..\Altair8800\mits_2sio.h"
 				>
 			</File>
+			<File
+				RelativePath="..\Altair8800\mits_acr.h"
+				>
+			</File>
 			<File
 				RelativePath="..\Altair8800\mits_dsk.h"
 				>
diff --git a/makefile b/makefile
index d83dd8bb..282a834e 100644
--- a/makefile
+++ b/makefile
@@ -2243,6 +2243,7 @@ ALTAIR8800 = \
     ${ALTAIR8800D}/s100_rom.c \
     ${ALTAIR8800D}/s100_z80.c \
     ${ALTAIR8800D}/mits_2sio.c \
+    ${ALTAIR8800D}/mits_acr.c \
     ${ALTAIR8800D}/mits_dsk.c \
     ${ALTAIR8800D}/sds_sbc200.c \
     ${ALTAIR8800D}/sds_vfii.c \