diff --git a/verilator/ide.cpp b/verilator/ide.cpp
new file mode 100644
index 0000000..8e0d58a
--- /dev/null
+++ b/verilator/ide.cpp
@@ -0,0 +1,294 @@
+#include "svdpi.h"
+#include "Vtest__Dpi.h"
+
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * simple IDE/ATA drive bus level emulation
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <fcntl.h>
+
+#ifdef unix
+#include <unistd.h>
+#endif
+
+#ifdef _WIN32
+typedef int off_t;
+#endif
+
+int last_evh;
+
+char last_dior_bit;
+char last_diow_bit;
+unsigned short last_read;
+
+int running_cver;
+
+static struct state_s {
+    unsigned short reg_seccnt, reg_secnum, reg_cyllow, reg_cylhigh, reg_drvhead;
+    unsigned short status;
+
+    int fifo_rd;
+    int fifo_wr;
+    int fifo_depth;
+    unsigned short fifo[256 * 128];
+
+    int file_inited;
+    int file_fd;
+
+    unsigned int lba;
+} state;
+
+#define ATA_ALTER    0x0e
+#define ATA_DEVCTRL  0x1e 
+#define ATA_DATA     0x10
+#define ATA_ERROR    0x11
+#define ATA_FEATURE  0x11
+#define ATA_SECCNT   0x12
+#define ATA_SECNUM   0x13
+#define ATA_CYLLOW   0x14
+#define ATA_CYLHIGH  0x15
+#define ATA_DRVHEAD  0x16
+#define ATA_STATUS   0x17
+#define ATA_COMMAND  0x17
+
+#define IDE_STATUS_BSY   7
+#define IDE_STATUS_DRDY  6
+#define IDE_STATUS_DWF   5
+#define IDE_STATUS_DSC   4
+#define IDE_STATUS_DRQ   3
+#define IDE_STATUS_CORR  2
+#define IDE_STATUS_IDX   1
+#define IDE_STATUS_ERR   0
+
+#define ATA_CMD_READ  0x0020
+#define ATA_CMD_WRITE  0x0030
+
+
+static void
+do_ide_setup(struct state_s *s)
+{
+    s->file_fd = open("rf.dsk", O_RDWR);
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC);
+    s->fifo_depth = 0;
+    s->fifo_rd = 0;
+    s->fifo_wr = 0;
+}
+
+static void
+do_ide_read(struct state_s *s)
+{
+    int ret;
+
+    s->lba =
+        ((s->reg_drvhead & 0x0f) << 24) |
+        ((s->reg_cylhigh & 0xff) << 16) |
+        ((s->reg_cyllow & 0xff) << 8) |
+        (s->reg_secnum & 0xff);
+
+    printf("dpi_ide: %d (lba %d), seccnt %d (read)\n",
+               s->lba*512, s->lba, s->reg_seccnt);
+
+    ret = lseek(s->file_fd, (off_t)s->lba*512, SEEK_SET);
+    ret = read(s->file_fd, (char *)s->fifo, 512 * s->reg_seccnt);
+    if (ret < 0)
+        perror("read");
+
+    printf("dpi_ide: buffer %06o %06o %06o %06o\n",
+               s->fifo[0], s->fifo[1], s->fifo[2], s->fifo[3]);
+
+    s->fifo_depth = (512 * s->reg_seccnt) / 2;
+    s->fifo_rd = 0;
+    s->fifo_wr = 0;
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC) | (1<<IDE_STATUS_DRQ);
+}
+
+static void
+do_ide_write(struct state_s *s)
+{
+    s->lba =
+        ((s->reg_drvhead & 0x0f) << 24) |
+        ((s->reg_cylhigh & 0xff) << 16) |
+        ((s->reg_cyllow & 0xff) << 8) |
+        (s->reg_secnum & 0xff);
+
+    if (0) printf("dpi_ide: %d (lba %d), seccnt %d (write)\n",
+               s->lba*512, s->lba, s->reg_seccnt);
+
+    printf("dpi_ide: write prep\n");
+
+    s->fifo_depth = (512 * s->reg_seccnt) / 2;
+    s->fifo_rd = 0;
+    s->fifo_wr = 0;
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC) | (1<<IDE_STATUS_DRQ);
+}
+
+static void
+do_ide_write_done(struct state_s *s)
+{
+    int ret;
+
+    printf("dpi_ide: %d (lba %d), seccnt %d (write)\n",
+              s->lba*512, s->lba, s->reg_seccnt);
+
+    ret = lseek(s->file_fd, (off_t)s->lba*512, SEEK_SET);
+    ret = write(s->file_fd, (char *)s->fifo, 512 * s->reg_seccnt);
+    if (ret < 0)
+        perror("write");
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC);
+}
+
+/*
+ *
+ */
+void dpi_ide(int data_in, int* data_out, int dior, int diow, int cs, int da)
+{
+    struct state_s *s;
+    int read_start, read_stop, write_start, write_stop;
+
+    s = &state;
+
+    if (!s->file_inited) {
+        s->file_inited = 1;
+        do_ide_setup(s);
+    }
+
+    /* */
+    read_start = 0;
+    read_stop = 0;
+    write_start = 0;
+    write_stop = 0;
+
+    if (dior != last_dior_bit) {
+        if (dior == 0) read_start = 1;
+        if (dior == 1) read_stop = 1;
+    }
+
+    if (diow != last_diow_bit) {
+        if (diow == 0) write_start = 1;
+        if (diow == 1) write_stop = 1;
+    }
+
+    last_dior_bit = dior;
+    last_diow_bit = diow;
+
+    if (0) {
+        if (read_start) printf("dpi_ide: read start\n");
+        if (read_stop) printf("dpi_ide: read stop\n");
+        if (write_start) printf("dpi_ide: write start\n");
+        if (write_stop) printf("dpi_ide: write stop\n");
+    }
+
+    /* */
+    if (write_start) {
+        if (0) printf("dpi_ide: write %x %x %d\n", cs, da, da);
+
+        switch (cs << 3 | da) {
+        case ATA_ALTER:
+        case ATA_DEVCTRL:
+            break;
+        case ATA_FEATURE:
+            break;
+
+        case ATA_SECCNT: s->reg_seccnt = data_in; break;
+        case ATA_SECNUM: s->reg_secnum = data_in; break;
+        case ATA_CYLLOW:
+            if (0) printf("dpi_ide: cyllow %04x\n", data_in);
+            s->reg_cyllow = data_in;
+            break;
+        case ATA_CYLHIGH:
+            if (0) printf("dpi_ide: cylhigh %04x\n", data_in);
+            s->reg_cylhigh = data_in;
+            break;
+        case ATA_DRVHEAD:
+            if (0) printf("dpi_ide: drvhead %04x\n", data_in);
+            s->reg_drvhead = data_in;
+            break;
+
+        case ATA_DATA:
+            s->fifo[s->fifo_wr] = data_in;
+
+            if (0) printf("dpi_ide: write data [%d/%d] %o\n",
+                              s->fifo_wr, s->fifo_depth, data_in);
+
+            if (s->fifo_wr < s->fifo_depth)
+                s->fifo_wr++;
+
+            if (s->fifo_wr >= s->fifo_depth) {
+                do_ide_write_done(s);
+            }
+            break;
+
+        case ATA_COMMAND:
+            printf("dpi_ide: command %04x\n", data_in);
+            switch (data_in) {
+            case 0x0020:
+                printf("dpi_ide: XXX READ\n");
+                do_ide_read(s);
+                break;
+            case 0x0030:
+                printf("dpi_ide: XXX WRITE\n");
+                do_ide_write(s);
+                break;
+            }
+            break;
+        }
+    }
+
+    if (read_start) {
+        if (0) printf("dpi_ide: read cs=%x da=%x %d\n", cs, da, da);
+
+        switch (cs << 3 | da) {
+        case ATA_DATA:
+            *data_out = last_read = s->fifo[s->fifo_rd];
+            if (0) printf("dpi_ide: read data [%d/%d] %o\n",
+                              s->fifo_rd, s->fifo_depth, *data_out);
+            if (s->fifo_rd < s->fifo_depth)
+                s->fifo_rd++;
+
+            if (s->fifo_rd >= s->fifo_depth) {
+                printf("dpi_ide: fifo empty\n");
+                s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC);
+            }
+            break;
+
+        case ATA_STATUS:
+            *data_out = last_read = s->status;
+            if (1) printf("dpi_ide: read status %04x\n", *data_out);
+            break;
+        }
+    }
+
+    if (!read_start && !write_start && dior == 0) {
+        if (0) printf("dpi_ide: read %04x\n", last_read);
+        *data_out = last_read;
+    }
+
+    if (read_stop) {
+    }
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+
+/*
+ * Local Variables:
+ * indent-tabs-mode:nil
+ * c-basic-offset:4
+ * End:
+*/
+
diff --git a/verilator/ide.cpp.1 b/verilator/ide.cpp.1
new file mode 100644
index 0000000..8e0d58a
--- /dev/null
+++ b/verilator/ide.cpp.1
@@ -0,0 +1,294 @@
+#include "svdpi.h"
+#include "Vtest__Dpi.h"
+
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * simple IDE/ATA drive bus level emulation
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <fcntl.h>
+
+#ifdef unix
+#include <unistd.h>
+#endif
+
+#ifdef _WIN32
+typedef int off_t;
+#endif
+
+int last_evh;
+
+char last_dior_bit;
+char last_diow_bit;
+unsigned short last_read;
+
+int running_cver;
+
+static struct state_s {
+    unsigned short reg_seccnt, reg_secnum, reg_cyllow, reg_cylhigh, reg_drvhead;
+    unsigned short status;
+
+    int fifo_rd;
+    int fifo_wr;
+    int fifo_depth;
+    unsigned short fifo[256 * 128];
+
+    int file_inited;
+    int file_fd;
+
+    unsigned int lba;
+} state;
+
+#define ATA_ALTER    0x0e
+#define ATA_DEVCTRL  0x1e 
+#define ATA_DATA     0x10
+#define ATA_ERROR    0x11
+#define ATA_FEATURE  0x11
+#define ATA_SECCNT   0x12
+#define ATA_SECNUM   0x13
+#define ATA_CYLLOW   0x14
+#define ATA_CYLHIGH  0x15
+#define ATA_DRVHEAD  0x16
+#define ATA_STATUS   0x17
+#define ATA_COMMAND  0x17
+
+#define IDE_STATUS_BSY   7
+#define IDE_STATUS_DRDY  6
+#define IDE_STATUS_DWF   5
+#define IDE_STATUS_DSC   4
+#define IDE_STATUS_DRQ   3
+#define IDE_STATUS_CORR  2
+#define IDE_STATUS_IDX   1
+#define IDE_STATUS_ERR   0
+
+#define ATA_CMD_READ  0x0020
+#define ATA_CMD_WRITE  0x0030
+
+
+static void
+do_ide_setup(struct state_s *s)
+{
+    s->file_fd = open("rf.dsk", O_RDWR);
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC);
+    s->fifo_depth = 0;
+    s->fifo_rd = 0;
+    s->fifo_wr = 0;
+}
+
+static void
+do_ide_read(struct state_s *s)
+{
+    int ret;
+
+    s->lba =
+        ((s->reg_drvhead & 0x0f) << 24) |
+        ((s->reg_cylhigh & 0xff) << 16) |
+        ((s->reg_cyllow & 0xff) << 8) |
+        (s->reg_secnum & 0xff);
+
+    printf("dpi_ide: %d (lba %d), seccnt %d (read)\n",
+               s->lba*512, s->lba, s->reg_seccnt);
+
+    ret = lseek(s->file_fd, (off_t)s->lba*512, SEEK_SET);
+    ret = read(s->file_fd, (char *)s->fifo, 512 * s->reg_seccnt);
+    if (ret < 0)
+        perror("read");
+
+    printf("dpi_ide: buffer %06o %06o %06o %06o\n",
+               s->fifo[0], s->fifo[1], s->fifo[2], s->fifo[3]);
+
+    s->fifo_depth = (512 * s->reg_seccnt) / 2;
+    s->fifo_rd = 0;
+    s->fifo_wr = 0;
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC) | (1<<IDE_STATUS_DRQ);
+}
+
+static void
+do_ide_write(struct state_s *s)
+{
+    s->lba =
+        ((s->reg_drvhead & 0x0f) << 24) |
+        ((s->reg_cylhigh & 0xff) << 16) |
+        ((s->reg_cyllow & 0xff) << 8) |
+        (s->reg_secnum & 0xff);
+
+    if (0) printf("dpi_ide: %d (lba %d), seccnt %d (write)\n",
+               s->lba*512, s->lba, s->reg_seccnt);
+
+    printf("dpi_ide: write prep\n");
+
+    s->fifo_depth = (512 * s->reg_seccnt) / 2;
+    s->fifo_rd = 0;
+    s->fifo_wr = 0;
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC) | (1<<IDE_STATUS_DRQ);
+}
+
+static void
+do_ide_write_done(struct state_s *s)
+{
+    int ret;
+
+    printf("dpi_ide: %d (lba %d), seccnt %d (write)\n",
+              s->lba*512, s->lba, s->reg_seccnt);
+
+    ret = lseek(s->file_fd, (off_t)s->lba*512, SEEK_SET);
+    ret = write(s->file_fd, (char *)s->fifo, 512 * s->reg_seccnt);
+    if (ret < 0)
+        perror("write");
+
+    s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC);
+}
+
+/*
+ *
+ */
+void dpi_ide(int data_in, int* data_out, int dior, int diow, int cs, int da)
+{
+    struct state_s *s;
+    int read_start, read_stop, write_start, write_stop;
+
+    s = &state;
+
+    if (!s->file_inited) {
+        s->file_inited = 1;
+        do_ide_setup(s);
+    }
+
+    /* */
+    read_start = 0;
+    read_stop = 0;
+    write_start = 0;
+    write_stop = 0;
+
+    if (dior != last_dior_bit) {
+        if (dior == 0) read_start = 1;
+        if (dior == 1) read_stop = 1;
+    }
+
+    if (diow != last_diow_bit) {
+        if (diow == 0) write_start = 1;
+        if (diow == 1) write_stop = 1;
+    }
+
+    last_dior_bit = dior;
+    last_diow_bit = diow;
+
+    if (0) {
+        if (read_start) printf("dpi_ide: read start\n");
+        if (read_stop) printf("dpi_ide: read stop\n");
+        if (write_start) printf("dpi_ide: write start\n");
+        if (write_stop) printf("dpi_ide: write stop\n");
+    }
+
+    /* */
+    if (write_start) {
+        if (0) printf("dpi_ide: write %x %x %d\n", cs, da, da);
+
+        switch (cs << 3 | da) {
+        case ATA_ALTER:
+        case ATA_DEVCTRL:
+            break;
+        case ATA_FEATURE:
+            break;
+
+        case ATA_SECCNT: s->reg_seccnt = data_in; break;
+        case ATA_SECNUM: s->reg_secnum = data_in; break;
+        case ATA_CYLLOW:
+            if (0) printf("dpi_ide: cyllow %04x\n", data_in);
+            s->reg_cyllow = data_in;
+            break;
+        case ATA_CYLHIGH:
+            if (0) printf("dpi_ide: cylhigh %04x\n", data_in);
+            s->reg_cylhigh = data_in;
+            break;
+        case ATA_DRVHEAD:
+            if (0) printf("dpi_ide: drvhead %04x\n", data_in);
+            s->reg_drvhead = data_in;
+            break;
+
+        case ATA_DATA:
+            s->fifo[s->fifo_wr] = data_in;
+
+            if (0) printf("dpi_ide: write data [%d/%d] %o\n",
+                              s->fifo_wr, s->fifo_depth, data_in);
+
+            if (s->fifo_wr < s->fifo_depth)
+                s->fifo_wr++;
+
+            if (s->fifo_wr >= s->fifo_depth) {
+                do_ide_write_done(s);
+            }
+            break;
+
+        case ATA_COMMAND:
+            printf("dpi_ide: command %04x\n", data_in);
+            switch (data_in) {
+            case 0x0020:
+                printf("dpi_ide: XXX READ\n");
+                do_ide_read(s);
+                break;
+            case 0x0030:
+                printf("dpi_ide: XXX WRITE\n");
+                do_ide_write(s);
+                break;
+            }
+            break;
+        }
+    }
+
+    if (read_start) {
+        if (0) printf("dpi_ide: read cs=%x da=%x %d\n", cs, da, da);
+
+        switch (cs << 3 | da) {
+        case ATA_DATA:
+            *data_out = last_read = s->fifo[s->fifo_rd];
+            if (0) printf("dpi_ide: read data [%d/%d] %o\n",
+                              s->fifo_rd, s->fifo_depth, *data_out);
+            if (s->fifo_rd < s->fifo_depth)
+                s->fifo_rd++;
+
+            if (s->fifo_rd >= s->fifo_depth) {
+                printf("dpi_ide: fifo empty\n");
+                s->status = (1<<IDE_STATUS_DRDY)|(1<<IDE_STATUS_DSC);
+            }
+            break;
+
+        case ATA_STATUS:
+            *data_out = last_read = s->status;
+            if (1) printf("dpi_ide: read status %04x\n", *data_out);
+            break;
+        }
+    }
+
+    if (!read_start && !write_start && dior == 0) {
+        if (0) printf("dpi_ide: read %04x\n", last_read);
+        *data_out = last_read;
+    }
+
+    if (read_stop) {
+    }
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+
+/*
+ * Local Variables:
+ * indent-tabs-mode:nil
+ * c-basic-offset:4
+ * End:
+*/
+
diff --git a/verilator/ram.cpp b/verilator/ram.cpp
new file mode 100644
index 0000000..babd989
--- /dev/null
+++ b/verilator/ram.cpp
@@ -0,0 +1,45 @@
+#include "svdpi.h"
+#include "Vtest_top__Dpi.h"
+
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+unsigned char ram_h[262144];
+unsigned char ram_l[262144];
+
+static int last_r;
+static int last_w;
+
+void dpi_ram (int a, int r, int w, int u, int l, int in, int* out)
+{
+	int o;
+	int assert_r, assert_w;
+
+	assert_r = r && !last_r;
+	assert_w = w && !last_w;
+
+	last_r = r;
+	last_w = w;
+
+	o = 0;
+	if (r) {
+		if (u) o |= ram_h[a] << 8;
+		if (l) o |= ram_l[a];
+		if (assert_r) printf("dpi_ram: read  [%o] -> %o\n", a, o);
+	}
+	*out = o;
+
+	if (w) {
+		if (u) ram_h[a] = in >> 8;
+		if (l) ram_l[a] = in;
+		if (assert_w) printf("dpi_ram: write  [%o] -> %o\n", a, in);
+	}
+}
+
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/verilator/test.cpp b/verilator/test.cpp
new file mode 100644
index 0000000..156548e
--- /dev/null
+++ b/verilator/test.cpp
@@ -0,0 +1,108 @@
+//
+// test.cpp
+//
+//
+
+#include <verilated.h>
+#include <verilated_vcd_c.h>
+#include "Vtest.h"
+
+#include <iostream>
+
+Vtest *top;                      // Instantiation of module
+
+unsigned int main_time = 0;     // Current simulation time
+
+double sc_time_stamp () {       // Called by $time in Verilog
+    return main_time;
+}
+
+int main(int argc, char** argv)
+{
+    VerilatedVcdC* tfp = NULL;
+    Verilated::commandArgs(argc, argv);   // Remember args
+
+    top = new Vtest;             // Create instance
+
+#ifdef VM_TRACE
+    if (0) {
+	    Verilated::traceEverOn(true);
+	    VL_PRINTF("Enabling waves...\n");
+	    tfp = new VerilatedVcdC;
+	    top->trace(tfp, 99);	// Trace 99 levels of hierarchy
+	    tfp->open("test.vcd");	// Open the dump file
+    }
+#endif
+
+    top->v__DOT__io__DOT__rf__DOT__buffer__DOT__ram_debug = 1;
+    top->v__DOT__sysclk = 0;
+
+    while (!Verilated::gotFinish()) {
+
+	// Resets
+	if (main_time < 500) {
+	    if (main_time == 20) {
+		    VL_PRINTF("reset on\n");
+		    top->v__DOT__reset = 1;
+		    top->v__DOT__initial_pc = 07400;
+	    }
+	    if (main_time == 50) {
+		    VL_PRINTF("reset off\n");
+		    top->v__DOT__reset = 0;
+	    }
+	}
+
+	// Toggle clock
+	top->v__DOT__sysclk = ~top->v__DOT__sysclk;
+
+	// Evaluate model
+        top->eval();
+
+        //if (top->v__DOT__sysclk) {
+	//printf("state %d\n", top->v__DOT__state);
+	//}
+
+        if (top->v__DOT__sysclk &&
+	    top->v__DOT__state == 1)
+	{
+		VL_PRINTF("pc %o ir %o l%d ac %o ion %o "
+			  "(IF%o DF%o UF%o SF%o IB%o UB%o) state %d\n",
+			  top->v__DOT__cpu__DOT__pc,
+			  top->v__DOT__mb,
+			  top->v__DOT__cpu__DOT__l,
+			  top->v__DOT__cpu__DOT__ac,
+			  top->v__DOT__cpu__DOT__interrupt_enable,
+			  top->v__DOT__cpu__DOT__IF,
+			  top->v__DOT__cpu__DOT__DF,
+			  top->v__DOT__cpu__DOT__UF,
+			  top->v__DOT__cpu__DOT__SF,
+			  top->v__DOT__cpu__DOT__IB,
+			  top->v__DOT__cpu__DOT__UB,
+			  top->v__DOT__state);
+	}
+
+#ifdef VM_TRACE
+//#define MIN_TIME 0
+//#define MAX_TIME 100000
+
+#define MIN_TIME 5196000
+#define MAX_TIME 5313000
+
+
+	if (tfp) {
+		if (main_time > MIN_TIME)
+			tfp->dump(main_time);
+
+		if (main_time > MAX_TIME)
+			vl_finish("test.cpp",__LINE__,"");
+	}
+#endif
+
+        main_time += 10;
+    }
+
+    top->final();
+
+    if (tfp)
+	    tfp->close();
+}