diff --git a/code/Makefile b/code/Makefile
index 9a2e85f..9ccddcc 100644
--- a/code/Makefile
+++ b/code/Makefile
@@ -1,5 +1,8 @@
-test.rim: main.rel tty.rel
-	ld6 -r 100 -o test.rim main.rel tty.rel
+test.rim: main.rel tty.rel pt.rel
+	ld6 -o test.rim main.rel tty.rel pt.rel
+
+test.sav: main.rel tty.rel pt.rel
+	ld6 -f sav -o test.sav main.rel tty.rel pt.rel
 
 %.rel: %.s
 	as6 -o $@ $<
diff --git a/code/main.s b/code/main.s
index 2dc994d..79de70b 100644
--- a/code/main.s
+++ b/code/main.s
@@ -8,8 +8,9 @@ PRS==4
 
 PTP==100
 
-EXTERNAL PUTC,PUTS
-EXTERNAL GETCH,GETC
+EXTERN PUTC,PUTS
+EXTERN GETCH,GETC
+EXTERN PTPUT
 
 ENTRY:	JRST	START
 
@@ -18,11 +19,11 @@ SP:	XWD	-100,PDL-1
 
 START:	MOVE	PDP,SP
 
-	UUO1	123
+;	UUO1	123
 
-	CONO	CPA,2001
-	CONO	PRS,2300
-	JRST	.
+;	CONO	CPA,2001
+;	CONO	PRS,2300
+;	JRST	.
 
 	MOVSI	AC2,440700
 	HRRI	AC2,MSG
@@ -35,11 +36,6 @@ START:	MOVE	PDP,SP
 
 	HALT
 
-PTPUT:	CONSZ	PTP,20
-	 JRST	.-1
-	DATAO	PTP,AC1
-	POPJ	PDP,
-
 MSG:	ASCIZ /Hello, world!
 yo! > /
 
diff --git a/emu/Makefile b/emu/Makefile
index a26aaf6..ad732d9 100644
--- a/emu/Makefile
+++ b/emu/Makefile
@@ -3,7 +3,7 @@ H=pdp6.h ../tools/pdp6common.h
 # clang
 #CFLAGS= -Wno-shift-op-parentheses -Wno-logical-op-parentheses \
 #        -Wno-bitwise-op-parentheses
-CFLAGS=  -g -fno-diagnostics-show-caret \
+CFLAGS=  -g -Wall -Wno-parentheses -fno-diagnostics-show-caret \
 	`sdl-config --cflags` `pkg-config SDL_image --cflags`
 
 LIBS=	`sdl-config --libs` `pkg-config SDL_image --libs` -lpthread
diff --git a/emu/apr.c b/emu/apr.c
index ead5d43..6e13d23 100644
--- a/emu/apr.c
+++ b/emu/apr.c
@@ -1,6 +1,49 @@
 #include "pdp6.h"
 #include <unistd.h>
 
+static void aprcycle(void *p);
+static void wake_cpa(void *dev);
+static void wake_pi(void *dev);
+
+void
+curpulse(Apr *apr, Pulse *p)
+{
+	if(apr->ncurpulses >= MAXPULSE){
+		fprint(stderr, "error: too many current pulses\n");
+		exit(1);
+	}
+	apr->clist[apr->ncurpulses++] = p;
+}
+
+void
+nextpulse(Apr *apr, Pulse *p)
+{
+	if(apr->nnextpulses >= MAXPULSE){
+		fprint(stderr, "error: too many next pulses\n");
+		exit(1);
+	}
+	apr->nlist[apr->nnextpulses++] = p;
+}
+
+Apr*
+makeapr(void)
+{
+	Apr *apr;
+	Thread th;
+
+	apr = malloc(sizeof(Apr));
+	memset(apr, 0, sizeof(Apr));
+	apr->iobus.dev[CPA] = (Busdev){ apr, wake_cpa, 0 };
+	apr->iobus.dev[PI] = (Busdev){ apr, wake_pi, 0 };
+
+	th = (Thread){ nil, aprcycle, apr, 1, 0 };
+	addthread(th);
+
+	return apr;
+}
+
+
+
 #define DBG_AR debug("AR: %012llo\n", apr->ar)
 #define DBG_MB debug("MB: %012llo\n", apr->mb)
 #define DBG_MQ debug("MQ: %012llo\n", apr->mq)
@@ -655,7 +698,7 @@ pulse(mr_pwr_clr){
 
 /* CPA and PI devices */
 
-void
+static void
 wake_cpa(void *dev)
 {
 	Apr *apr;
@@ -708,7 +751,7 @@ wake_cpa(void *dev)
 		ex_set(apr);
 }
 
-void
+static void
 wake_pi(void *dev)
 {
 	Apr *apr;
@@ -2487,9 +2530,9 @@ pulse(et0a){
 	trace("ET0A\n");
 	debug("%o: ", apr->pc);
 	if((apr->inst & 0700) != 0700)
-		debug("%s\n", names[apr->inst]);
+		debug("%s\n", mnemonics[apr->inst]);
 	else
-		debug("%s\n", ionames[apr->io_inst>>5 & 7]);
+		debug("%s\n", iomnemonics[apr->io_inst>>5 & 7]);
 
 	if(PI_HOLD)
 		set_pih(apr, apr->pi_req);	// 8-3, 8-4
@@ -3014,36 +3057,6 @@ pulse(key_manual){
 	nextpulse(apr, kt0);		// 5-2
 }
 
-void
-curpulse(Apr *apr, Pulse *p)
-{
-	if(apr->ncurpulses >= MAXPULSE){
-		fprint(stderr, "error: too many current pulses\n");
-		exit(1);
-	}
-	apr->clist[apr->ncurpulses++] = p;
-}
-
-void
-nextpulse(Apr *apr, Pulse *p)
-{
-	if(apr->nnextpulses >= MAXPULSE){
-		fprint(stderr, "error: too many next pulses\n");
-		exit(1);
-	}
-	apr->nlist[apr->nnextpulses++] = p;
-}
-
-Apr*
-makeapr(void)
-{
-	Apr *apr;
-	apr = malloc(sizeof(Apr));
-	memset(apr, 0, sizeof(Apr));
-	apr->iobus.dev[CPA] = (Busdev){ apr, wake_cpa, 0 };
-	apr->iobus.dev[PI] = (Busdev){ apr, wake_pi, 0 };
-	return apr;
-}
 
 /* find out which bits were turned on */
 void
@@ -3057,16 +3070,10 @@ updatebus(void *bus)
 
 #define TIMESTEP (1000.0/60.0)
 
-void*
-aprmain(void *p)
+void
+aprstart(Apr *apr)
 {
-	Apr *apr;
-	Busdev *dev;
-	Pulse **tmp;
-	int i, devcode;
-	double lasttick, tick;
-
-	apr = (Apr*)p;
+	printf("[aprstart]\n");
 	apr->clist = apr->pulses1;
 	apr->nlist = apr->pulses2;
 	apr->ncurpulses = 0;
@@ -3080,262 +3087,144 @@ aprmain(void *p)
 	apr->membus.c34 = 0;
 	apr->iobus.c12 = 0;
 	apr->iobus.c34 = 0;
-	if(apr->membus.fmem)
-		apr->membus.fmem->poweron(apr->membus.fmem);
-	for(i = 0; i < 16; i++)
-		if(apr->membus.cmem[i])
-			apr->membus.cmem[i]->poweron(apr->membus.cmem[i]);
 
 	nextpulse(apr, mr_pwr_clr);
-	lasttick = getms();
-	while(apr->sw_power){
-		apr->ncurpulses = apr->nnextpulses;
-		apr->nnextpulses = 0;
-		tmp = apr->clist; apr->clist = apr->nlist; apr->nlist = tmp;
+	apr->lasttick = getms();
+	apr->powered = 1;
+}
 
-		if(apr->pulsestepping){
-			int c;
-			while(c = getchar(), c != EOF && c != '\n')
-				if(c == 'x')
-					apr->pulsestepping = 0;
-		}
+static void
+aprcycle(void *p)
+{
+	Apr *apr;
+	Busdev *dev;
+	Pulse **tmp;
+	int i, devcode;
 
-		tick = getms();
-		if(tick-lasttick >= TIMESTEP){
-			lasttick = lasttick+TIMESTEP;
-			apr->cpa_clock_flag = 1;
-			recalc_cpa_req(apr);
-		}
+	apr = p;
 
-		apr->iobus.c12_prev = apr->iobus.c12;
-		apr->iobus.c34_prev = apr->iobus.c34;
-		apr->membus.c12_prev = apr->membus.c12;
-		apr->membus.c34_prev = apr->membus.c34;
+	if(!apr->sw_power){
+		apr->powered = 0;
+		return;
+	}else if(!apr->powered)
+		aprstart(apr);
 
-		for(i = 0; i < apr->ncurpulses; i++)
-			apr->clist[i](apr);
+	apr->ncurpulses = apr->nnextpulses;
+	apr->nnextpulses = 0;
+	tmp = apr->clist; apr->clist = apr->nlist; apr->nlist = tmp;
 
-		updatebus(&apr->iobus);
-		updatebus(&apr->membus);
+	if(apr->pulsestepping){
+		int c;
+		while(c = getchar(), c != EOF && c != '\n')
+			if(c == 'x')
+				apr->pulsestepping = 0;
+	}
 
-		/* This is simplified, we have no IOT RESET,
-		 * IOT INIT SET UP or IOT FINAL SETUP really.
-		 * normally we'd have to wait for IOT RESET to clear here */
-		if(apr->iot_go)
-			nextpulse(apr, iot_t2);
+	apr->tick = getms();
+	if(apr->tick-apr->lasttick >= TIMESTEP){
+		apr->lasttick = apr->lasttick+TIMESTEP;
+		apr->cpa_clock_flag = 1;
+		recalc_cpa_req(apr);
+	}
+
+	apr->iobus.c12_prev = apr->iobus.c12;
+	apr->iobus.c34_prev = apr->iobus.c34;
+	apr->membus.c12_prev = apr->membus.c12;
+	apr->membus.c34_prev = apr->membus.c34;
+
+	for(i = 0; i < apr->ncurpulses; i++)
+		apr->clist[i](apr);
+
+	updatebus(&apr->iobus);
+	updatebus(&apr->membus);
+
+	/* This is simplified, we have no IOT RESET,
+	 * IOT INIT SET UP or IOT FINAL SETUP really.
+	 * normally we'd have to wait for IOT RESET to clear here */
+	if(apr->iot_go)
+		nextpulse(apr, iot_t2);
 
 
-		/* Key pulses */
-		if(apr->extpulse & EXT_KEY_MANUAL){
-			apr->extpulse &= ~EXT_KEY_MANUAL;
-			nextpulse(apr, key_manual);
-		}
-		if(apr->extpulse & EXT_KEY_INST_STOP){
-			apr->extpulse &= ~EXT_KEY_INST_STOP;
-			apr->run = 0;
-			// hack: cleared when the pulse list was empty
-			apr->ia_inh = 1;
-		}
+	/* Key pulses */
+	if(apr->extpulse & EXT_KEY_MANUAL){
+		apr->extpulse &= ~EXT_KEY_MANUAL;
+		nextpulse(apr, key_manual);
+	}
+	if(apr->extpulse & EXT_KEY_INST_STOP){
+		apr->extpulse &= ~EXT_KEY_INST_STOP;
+		apr->run = 0;
+		// hack: cleared when the pulse list was empty
+		apr->ia_inh = 1;
+	}
 
 
-		/* Pulses and signals through IO bus */
-		apr->iobus.devcode = -1;
-		if(apr->iobus.c34_pulse & (IOBUS_PULSES | IOBUS_IOB_STATUS | IOBUS_IOB_DATAI)){
-			devcode = 0;
-			if(apr->iobus.c34 & IOBUS_IOS3_1) devcode |= 0100;
-			if(apr->iobus.c34 & IOBUS_IOS4_1) devcode |= 0040;
-			if(apr->iobus.c34 & IOBUS_IOS5_1) devcode |= 0020;
-			if(apr->iobus.c34 & IOBUS_IOS6_1) devcode |= 0010;
-			if(apr->iobus.c34 & IOBUS_IOS7_1) devcode |= 0004;
-			if(apr->iobus.c34 & IOBUS_IOS8_1) devcode |= 0002;
-			if(apr->iobus.c34 & IOBUS_IOS9_1) devcode |= 0001;
-			apr->iobus.devcode = devcode;
-			dev = &apr->iobus.dev[devcode];
+	/* Pulses and signals through IO bus */
+	apr->iobus.devcode = -1;
+	if(apr->iobus.c34_pulse & (IOBUS_PULSES | IOBUS_IOB_STATUS | IOBUS_IOB_DATAI)){
+		devcode = 0;
+		if(apr->iobus.c34 & IOBUS_IOS3_1) devcode |= 0100;
+		if(apr->iobus.c34 & IOBUS_IOS4_1) devcode |= 0040;
+		if(apr->iobus.c34 & IOBUS_IOS5_1) devcode |= 0020;
+		if(apr->iobus.c34 & IOBUS_IOS6_1) devcode |= 0010;
+		if(apr->iobus.c34 & IOBUS_IOS7_1) devcode |= 0004;
+		if(apr->iobus.c34 & IOBUS_IOS8_1) devcode |= 0002;
+		if(apr->iobus.c34 & IOBUS_IOS9_1) devcode |= 0001;
+		apr->iobus.devcode = devcode;
+		dev = &apr->iobus.dev[devcode];
+		if(dev->wake)
+			dev->wake(dev->dev);
+	}
+	if(apr->iobus.c34_pulse & IOBUS_IOB_RESET){
+		int d;
+		for(d = 0; d < 128; d++){
+			dev = &apr->iobus.dev[d];
 			if(dev->wake)
 				dev->wake(dev->dev);
 		}
-		if(apr->iobus.c34_pulse & IOBUS_IOB_RESET){
-			int d;
-			for(d = 0; d < 128; d++){
-				dev = &apr->iobus.dev[d];
-				if(dev->wake)
-					dev->wake(dev->dev);
-			}
-		}
-		apr->iobus.c34 &= ~(IOBUS_PULSES | IOBUS_IOB_RESET);
-
-		/* Pulses to memory */
-		if(apr->membus.c12_pulse & (MEMBUS_WR_RS | MEMBUS_RQ_CYC)){
-			wakemem(&apr->membus);
-			apr->membus.c12 &= ~MEMBUS_WR_RS;
-		}
-
-		/* Pulses from memory  */
-		if(apr->membus.c12 & MEMBUS_MAI_ADDR_ACK){
-			apr->membus.c12 &= ~MEMBUS_MAI_ADDR_ACK;
-			apr->extpulse &= ~EXT_NONEXIT_MEM;
-			nextpulse(apr, mai_addr_ack);
-		}
-		if(apr->membus.c12 & MEMBUS_MAI_RD_RS){
-			apr->membus.c12 &= ~MEMBUS_MAI_RD_RS;
-			nextpulse(apr, mai_rd_rs);
-		}
-		if(apr->mc_rd && apr->membus.c34){
-			/* 7-6, 7-9 */
-			apr->mb |= apr->membus.c34;
-			apr->membus.c34 = 0;
-		}
-
-		/* TODO: do this differently because the
-		 * memory might have been busy. */
-		if(apr->extpulse & EXT_NONEXIT_MEM){
-			apr->extpulse &= ~EXT_NONEXIT_MEM;
-			if(apr->mc_rq && !apr->mc_stop)
-				nextpulse(apr, mc_non_exist_mem);	// 7-9
-		}
-
-		if(i)
-			trace("--------------\n");
-		else
-			/* no longer needed */
-			apr->ia_inh = 0;
 	}
-	debug("power off\n");
-	return nil;
+	apr->iobus.c34 &= ~(IOBUS_PULSES | IOBUS_IOB_RESET);
+
+	/* Pulses to memory */
+	if(apr->membus.c12_pulse & (MEMBUS_WR_RS | MEMBUS_RQ_CYC)){
+		wakemem(&apr->membus);
+		apr->membus.c12 &= ~MEMBUS_WR_RS;
+	}
+
+	/* Pulses from memory  */
+	if(apr->membus.c12 & MEMBUS_MAI_ADDR_ACK){
+		apr->membus.c12 &= ~MEMBUS_MAI_ADDR_ACK;
+		apr->extpulse &= ~EXT_NONEXIT_MEM;
+		nextpulse(apr, mai_addr_ack);
+	}
+	if(apr->membus.c12 & MEMBUS_MAI_RD_RS){
+		apr->membus.c12 &= ~MEMBUS_MAI_RD_RS;
+		nextpulse(apr, mai_rd_rs);
+	}
+	if(apr->mc_rd && apr->membus.c34){
+		/* 7-6, 7-9 */
+		apr->mb |= apr->membus.c34;
+		apr->membus.c34 = 0;
+	}
+
+	/* TODO: do this differently because the
+	 * memory might have been busy. */
+	if(apr->extpulse & EXT_NONEXIT_MEM){
+		apr->extpulse &= ~EXT_NONEXIT_MEM;
+		if(apr->mc_rq && !apr->mc_stop)
+			nextpulse(apr, mc_non_exist_mem);	// 7-9
+	}
+
+	if(i)
+		trace("--------------\n");
+	else
+		/* no longer needed */
+		apr->ia_inh = 0;
 }
 
 
-char *names[0700] = {
-	"UUO00", "UUO01", "UUO02", "UUO03",
-	"UUO04", "UUO05", "UUO06", "UUO07",
-	"UUO10", "UUO11", "UUO12", "UUO13",
-	"UUO14", "UUO15", "UUO16", "UUO17",
-	"UUO20", "UUO21", "UUO22", "UUO23",
-	"UUO24", "UUO25", "UUO26", "UUO27",
-	"UUO30", "UUO31", "UUO32", "UUO33",
-	"UUO34", "UUO35", "UUO36", "UUO37",
-	"UUO40", "UUO41", "UUO42", "UUO43",
-	"UUO44", "UUO45", "UUO46", "UUO47",
-	"UUO50", "UUO51", "UUO52", "UUO53",
-	"UUO54", "UUO55", "UUO56", "UUO57",
-	"UUO60", "UUO61", "UUO62", "UUO63",
-	"UUO64", "UUO65", "UUO66", "UUO67",
-	"UUO70", "UUO71", "UUO72", "UUO73",
-	"UUO74", "UUO75", "UUO76", "UUO77",
 
-	"XX100", "XX101", "XX102", "XX103",
-	"XX104", "XX105", "XX106", "XX107",
-	"XX110", "XX111", "XX112", "XX113",
-	"XX114", "XX115", "XX116", "XX117",
-	"XX120", "XX121", "XX122", "XX123",
-	"XX124", "XX125", "XX126", "XX127",
-	"XX130", "XX131", "FSC", "CAO",
-	"LDCI", "LDC", "DPCI", "DPC",
-	"FAD", "FADL", "FADM", "FADB",
-	"FADR", "FADLR", "FADMR", "FADBR",
-	"FSB", "FSBL", "FSBM", "FSBB",
-	"FSBR", "FSBLR", "FSBMR", "FSBBR",
-	"FMP", "FMPL", "FMPM", "FMPB",
-	"FMPR", "FMPLR", "FMPMR", "FMPBR",
-	"FDV", "FDVL", "FDVM", "FDVB",
-	"FDVR", "FDVLR", "FDVMR", "FDVBR",
 
-	"MOVE", "MOVEI", "MOVEM", "MOVES",
-	"MOVS", "MOVSI", "MOVSM", "MOVSS",
-	"MOVN", "MOVNI", "MOVNM", "MOVNS",
-	"MOVM", "MOVMI", "MOVMM", "MOVMS",
-	"IMUL", "IMULI", "IMULM", "IMULB",
-	"MUL", "MULI", "MULM", "MULB",
-	"IDIV", "IDIVI", "IDIVM", "IDIVB",
-	"DIV", "DIVI", "DIVM", "DIVB",
-	"ASH", "ROT", "LSH", "XX243",
-	"ASHC", "ROTC", "LSHC", "XX247",
-	"EXCH", "BLT", "AOBJP", "AOBJN",
-	"JRST", "JFCL", "XCT", "XX257",
-	"PUSHJ", "PUSH", "POP", "POPJ",
-	"JSR", "JSP", "JSA", "JRA",
-	"ADD", "ADDI", "ADDM", "ADDB",
-	"SUB", "SUBI", "SUBM", "SUBB",
 
-	"CAI", "CAIL", "CAIE", "CAILE",
-	"CAIA", "CAIGE", "CAIN", "CAIG",
-	"CAM", "CAML", "CAME", "CAMLE",
-	"CAMA", "CAMGE", "CAMN", "CAMG",
-	"JUMP", "JUMPL", "JUMPE", "JUMPLE",
-	"JUMPA", "JUMPGE", "JUMPN", "JUMPG",
-	"SKIP", "SKIPL", "SKIPE", "SKIPLE",
-	"SKIPA", "SKIPGE", "SKIPN", "SKIPG",
-	"AOJ", "AOJL", "AOJE", "AOJLE",
-	"AOJA", "AOJGE", "AOJN", "AOJG",
-	"AOS", "AOSL", "AOSE", "AOSLE",
-	"AOSA", "AOSGE", "AOSN", "AOSG",
-	"SOJ", "SOJL", "SOJE", "SOJLE",
-	"SOJA", "SOJGE", "SOJN", "SOJG",
-	"SOS", "SOSL", "SOSE", "SOSLE",
-	"SOSA", "SOSGE", "SOSN", "SOSG",
-
-	"SETZ", "SETZI", "SETZM", "SETZB",
-	"AND", "ANDI", "ANDM", "ANDB",
-	"ANDCA", "ANDCAI", "ANDCAM", "ANDCAB",
-	"SETM", "SETMI", "SETMM", "SETMB",
-	"ANDCM", "ANDCMI", "ANDCMM", "ANDCMB",
-	"SETA", "SETAI", "SETAM", "SETAB",
-	"XOR", "XORI", "XORM", "XORB",
-	"IOR", "IORI", "IORM", "IORB",
-	"ANDCB", "ANDCBI", "ANDCBM", "ANDCBB",
-	"EQV", "EQVI", "EQVM", "EQVB",
-	"SETCA", "SETCAI", "SETCAM", "SETCAB",
-	"ORCA", "ORCAI", "ORCAM", "ORCAB",
-	"SETCM", "SETCMI", "SETCMM", "SETCMB",
-	"ORCM", "ORCMI", "ORCMM", "ORCMB",
-	"ORCB", "ORCBI", "ORCBM", "ORCBB",
-	"SETO", "SETOI", "SETOM", "SETOB",
-
-	"HLL", "HLLI", "HLLM", "HLLS",
-	"HRL", "HRLI", "HRLM", "HRLS",
-	"HLLZ", "HLLZI", "HLLZM", "HLLZS",
-	"HRLZ", "HRLZI", "HRLZM", "HRLZS",
-	"HLLO", "HLLOI", "HLLOM", "HLLOS",
-	"HRLO", "HRLOI", "HRLOM", "HRLOS",
-	"HLLE", "HLLEI", "HLLEM", "HLLES",
-	"HRLE", "HRLEI", "HRLEM", "HRLES",
-	"HRR", "HRRI", "HRRM", "HRRS",
-	"HLR", "HLRI", "HLRM", "HLRS",
-	"HRRZ", "HRRZI", "HRRZM", "HRRZS",
-	"HLRZ", "HLRZI", "HLRZM", "HLRZS",
-	"HRRO", "HRROI", "HRROM", "HRROS",
-	"HLRO", "HLROI", "HLROM", "HLROS",
-	"HRRE", "HRREI", "HRREM", "HRRES",
-	"HLRE", "HLREI", "HLREM", "HLRES",
-
-	"TRN", "TLN", "TRNE", "TLNE",
-	"TRNA", "TLNA", "TRNN", "TLNN",
-	"TDN", "TSN", "TDNE", "TSNE",
-	"TDNA", "TSNA", "TDNN", "TSNN",
-	"TRZ", "TLZ", "TRZE", "TLZE",
-	"TRZA", "TLZA", "TRZN", "TLZN",
-	"TDZ", "TSZ", "TDZE", "TSZE",
-	"TDZA", "TSZA", "TDZN", "TSZN",
-	"TRC", "TLC", "TRCE", "TLCE",
-	"TRCA", "TLCA", "TRCN", "TLCN",
-	"TDC", "TSC", "TDCE", "TSCE",
-	"TDCA", "TSCA", "TDCN", "TSCN",
-	"TRO", "TLO", "TROE", "TLOE",
-	"TROA", "TLOA", "TRON", "TLON",
-	"TDO", "TSO", "TDOE", "TSOE",
-	"TDOA", "TSOA", "TDON", "TSON",
-};
-
-char *ionames[] = {
-	"BLKI",
-	"DATAI",
-	"BLKO",
-	"DATAO",
-	"CONO",
-	"CONI",
-	"CONSZ",
-	"CONSO"
-};
 
 void
 testinst(Apr *apr)
@@ -3346,7 +3235,7 @@ testinst(Apr *apr)
 //	for(inst = 0140; inst < 0141; inst++){
 		apr->ir = inst << 9 | 1 << 5;
 		decodeir(apr);
-		debug("%06o %6s ", apr->ir, names[inst]);
+		debug("%06o %6s ", apr->ir, mnemonics[inst]);
 /*
 		debug("%s ", FAC_INH ? "FAC_INH" : "       ");
 		debug("%s ", FAC2 ? "FAC2" : "    ");
@@ -3360,8 +3249,8 @@ testinst(Apr *apr)
 		debug("%s ", SAC2 ? "SAC2" : "    ");
 		debug("\n");
 // FC_E_PSE
-//debug("FC_E_PSE: %d %d %d %d %d %d %d %d %d %d\n", apr->hwt_10 , apr->hwt_11 , apr->fwt_11 , \
-//                  IOT_BLK , apr->inst == EXCH , CH_DEP , CH_INC_OP , \
+//debug("FC_E_PSE: %d %d %d %d %d %d %d %d %d %d\n", apr->hwt_10 , apr->hwt_11 , apr->fwt_11 ,
+//                  IOT_BLK , apr->inst == EXCH , CH_DEP , CH_INC_OP ,
 //                  MEMAC_MEM , apr->boole_as_10 , apr->boole_as_11);
 //debug("CH: %d %d %d %d %d\n", CH_INC, CH_INC_OP, CH_N_INC_OP, CH_LOAD, CH_DEP);
 //debug("FAC_INH: %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n",
diff --git a/emu/cmd.c b/emu/cmd.c
index 2e8148c..445e174 100644
--- a/emu/cmd.c
+++ b/emu/cmd.c
@@ -200,7 +200,7 @@ dep(word addr, int fastmem, word w)
 static void
 c_ex(int argc, char *argv[])
 {
-	char *argv0;
+	char *argv0 = nil;
 	word start, end;
 	int format, fastmem;
 
@@ -225,7 +225,7 @@ c_ex(int argc, char *argv[])
 static void
 c_dep(int argc, char *argv[])
 {
-	char *argv0;
+	char *argv0 = nil;
 	word start, end;
 	word w;
 	int fastmem;
@@ -276,6 +276,7 @@ loadsav(FILE *fp)
 static void
 c_load(int argc, char *argv[])
 {
+	char *argv0 = nil;
 	FILE *fp;
 	int fmt;
 
diff --git a/emu/main.c b/emu/main.c
index 5ea088b..2a74e46 100644
--- a/emu/main.c
+++ b/emu/main.c
@@ -74,6 +74,26 @@ err(char *fmt, ...)
 	exit(1);
 }
 
+u32
+getms(void)
+{
+	return SDL_GetTicks();
+}
+
+int
+hasinput(int fd)
+{
+	fd_set fds;
+	struct timeval timeout;
+
+	timeout.tv_sec = 0;
+	timeout.tv_usec = 0;
+	FD_ZERO(&fds);
+	FD_SET(fd, &fds);
+	return select(fd+1, &fds, NULL, NULL, &timeout) > 0;
+}
+
+
 SDL_Surface*
 mustloadimg(const char *path)
 {
@@ -141,14 +161,6 @@ getswitches(Element *sw, int n)
 	return w;
 }
 
-void
-poweron(Apr *apr)
-{
-	pthread_t apr_thread;
-	apr->sw_power = 1;
-	pthread_create(&apr_thread, nil, aprmain, apr);
-}
-
 #define KEYPULSE(k) (apr->k && !oldapr.k)
 
 void
@@ -170,8 +182,6 @@ updateapr(Apr *apr, Ptr *ptr)
 	misc_l[3].state = apr->sw_repeat = misc_sw[0].state;
 	misc_l[4].state = apr->sw_addr_stop = misc_sw[1].state;
 	misc_l[5].state = apr->sw_power = misc_sw[2].state;
-	if(apr->sw_power && !oldapr.sw_power)
-		poweron(apr);
 	misc_l[6].state = apr->sw_mem_disable = misc_sw[3].state;
 	apr->data = getswitches(data_sw, 36);
 	apr->mas = getswitches(ma_sw, 18);
@@ -528,12 +538,38 @@ findlayout(int *w, int *h)
 	*h = oppanel.pos.y + oppanel.surf->h;
 }
 
-u32
-getms(void)
+
+Thread *threads;
+
+void
+addthread(Thread th)
 {
-	return SDL_GetTicks();
+	Thread *p;
+	p = malloc(sizeof(Thread));
+	*p = th;
+	p->next = threads;
+	threads = p;
 }
 
+void*
+simthread(void *p)
+{
+	Thread *th;
+
+	printf("[simthread] start\n");
+	for(;;)
+		for(th = threads; th; th = th->next){
+			th->cnt++;
+			if(th->cnt == th->freq){
+				th->cnt = 0;
+				th->f(th->arg);
+			}
+		}
+	err("can't happen");
+	return nil;
+}
+
+
 void
 quit(int code)
 {
@@ -550,7 +586,6 @@ usage(void)
 }
 
 Apr *aprs[4];
-Mem *coremems[4];
 
 int
 main(int argc, char *argv[])
@@ -560,17 +595,17 @@ main(int argc, char *argv[])
 	SDL_MouseButtonEvent *mbev;
 	SDL_MouseMotionEvent *mmev;
 	Element *e;
-	Uint32 start, end;
-	int delay;
 	int i;
 	int w, h;
-	pthread_t cmd_thread;
+	pthread_t cmd_thread, sim_thread;
 	const char *outfile, *ttyfile;
 
 	Apr *apr;
 	Ptr *ptr;
 	Ptp *ptp;
 	Tty *tty;
+	Mem *coremems[4];
+	Mem *fastmem;
 
 	outfile = "/dev/null";
 	ttyfile = "/tmp/6tty";
@@ -681,12 +716,14 @@ main(int argc, char *argv[])
 
 	extra_l = e; e += 1;
 
-	aprs[0] = apr = makeapr();
+	fastmem = makefastmem(0);
 	coremems[0] = makecoremem("mem_0");
 	coremems[1] = makecoremem("mem_1");
 	coremems[2] = makecoremem("mem_2");
 	coremems[3] = makecoremem("mem_3");
-	attachmem(makefastmem(0), 0, &apr->membus, -1);
+
+	aprs[0] = apr = makeapr();
+	attachmem(fastmem, 0, &apr->membus, -1);
 	attachmem(coremems[0], 0, &apr->membus, 0);
 	attachmem(coremems[1], 0, &apr->membus, 1);
 	attachmem(coremems[2], 0, &apr->membus, 2);
@@ -697,10 +734,18 @@ main(int argc, char *argv[])
 	if(ttyfile)
 		attachdevtty(tty, ttyfile);
 
+	/* Power on memory */
+	// TODO: maybe do that somewhere else?
+	fastmem->poweron(fastmem);
+	coremems[0]->poweron(coremems[0]);
+	coremems[1]->poweron(coremems[1]);
+	coremems[2]->poweron(coremems[2]);
+	coremems[3]->poweron(coremems[3]);
+
+	pthread_create(&sim_thread, nil, simthread, apr);
 	pthread_create(&cmd_thread, nil, cmdthread, nil);
 
 	for(;;){
-		start = SDL_GetTicks();
 		while(SDL_PollEvent(&ev))
 			switch(ev.type){
 			case SDL_MOUSEMOTION:
@@ -744,10 +789,6 @@ main(int argc, char *argv[])
 //		SDL_UnlockSurface(screen);
 
 		SDL_Flip(screen);
-		end = SDL_GetTicks();
-		delay =  (1000 / 30) - (end-start);
-//		if(delay > 0)
-//			SDL_Delay(delay);
 	}
 	return 0;
 }
diff --git a/emu/mem.c b/emu/mem.c
index f7361a6..b340c80 100644
--- a/emu/mem.c
+++ b/emu/mem.c
@@ -46,7 +46,6 @@ wakecore(Mem *mem, Membus *bus)
 	 * Lower numbers have higher priority but proc 2 and 3 have
 	 * the same priority and requests are alternated between them.
 	 * If no request is made, we should already be connected to a bus */
-	pthread_mutex_lock(&core->mutex);
 	if(core->cmc_p_act < 0){
 		if(mem->bus[0]->c12 & MEMBUS_RQ_CYC)
 			core->cmc_p_act = 0;
@@ -65,18 +64,16 @@ wakecore(Mem *mem, Membus *bus)
 					core->cmc_p_act = 2;
 				else if(p3)
 					core->cmc_p_act = 3;
-				else{
-					pthread_mutex_unlock(&core->mutex);
+				else
 					return 1;	/* no request at all? */
-				}
 			}
 			core->cmc_last_proc = core->cmc_p_act;
 		}
 	}
-	pthread_mutex_unlock(&core->mutex);
 
 	/* The executing thread can only service requests from its own processor
 	 * due to synchronization with the processor's pulse cycle. */
+	/* TODO: is this still true after the removal of pthreads? */
 	if(bus != mem->bus[core->cmc_p_act])
 		return 1;
 
@@ -135,6 +132,7 @@ powercore(Mem *mem)
 {
 	CMem *core;
 
+	printf("[powercore]\n");
 	core = mem->module;
 	readmem(core->filename, core->core, 040000);
 	core->cmc_aw_rq = 1;
@@ -200,6 +198,7 @@ powerff(Mem *mem)
 {
 	FMem *ff;
 
+	printf("[powerff]\n");
 	ff = mem->module;
 	ff->fmc_act = 0;
 	ff->fmc_wr = 0;
@@ -241,7 +240,6 @@ makecoremem(const char *file)
 	core = malloc(sizeof(CMem));
 	memset(core, 0, sizeof(CMem));
 	core->filename = file;
-	pthread_mutex_init(&core->mutex, nil);
 
 	mem = malloc(sizeof(Mem));
 	mem->module = core;
diff --git a/emu/pdp6.h b/emu/pdp6.h
index 5c38a47..165d89e 100644
--- a/emu/pdp6.h
+++ b/emu/pdp6.h
@@ -5,7 +5,6 @@
 #include <string.h>
 #include <ctype.h>
 #include <assert.h>
-#include <pthread.h>
 #include "../tools/pdp6common.h"
 
 #define nelem(a) (sizeof(a)/sizeof(a[0]))
@@ -24,6 +23,9 @@ extern FILE *debugfp;
 extern int dotrace;
 void trace(char *fmt, ...);
 void debug(char *fmt, ...);
+void err(char *fmt, ...);
+u32 getms(void);
+int hasinput(int fd);
 
 void quit(int code);
 void *cmdthread(void *);
@@ -65,6 +67,20 @@ enum FullwordBits {
 	F33 = 0000000000004, F34 = 0000000000002, F35 = 0000000000001
 };
 
+typedef struct Thread Thread;
+struct Thread
+{
+	Thread *next;	/* link to next thread */
+	void (*f)(void*);
+	void *arg;
+	int freq;	/* how often the thread is serviced */
+	int cnt;
+};
+
+extern Thread *threads;
+void addthread(Thread th);
+
+
 /* external pulses, bits of Apr.extpulse */
 enum Extpulse {
 	EXT_KEY_MANUAL       = 1,
@@ -121,8 +137,6 @@ typedef struct Busdev Busdev;
 typedef struct IOBus IOBus;
 typedef struct Apr Apr;
 
-u32 getms(void);
-
 
 /*
  * Memory
@@ -190,7 +204,6 @@ Mem *makefastmem(int p);
 struct CMem
 {
 	const char *filename;
-	pthread_mutex_t mutex;
 
 	word core[040000];
 	word cmb;
@@ -294,6 +307,7 @@ struct Apr
 {
 	IOBus iobus;
 	Membus membus;
+	int powered;
 
 	hword ir;
 	word mi;
@@ -391,6 +405,7 @@ struct Apr
 	bool pc_set;
 
 	/* needed for the emulation */
+	double lasttick, tick;
 	int extpulse;
 	bool ia_inh;	// this is asserted for some time
 	int pulsestepping;
@@ -401,9 +416,6 @@ struct Apr
 };
 extern Apr *aprs[4];
 Apr *makeapr(void);
-void curpulse(Apr *apr, Pulse *p);
-void nextpulse(Apr *apr, Pulse *p);
-void *aprmain(void *p);
 
 
 /* Paper tape punch 761 */
@@ -416,7 +428,7 @@ struct Ptp
 	bool busy, flag, b;
 	int pia;
 
-	FILE *fp;
+	int fd;
 	int waitdatao;
 };
 Ptp *makeptp(IOBus *bus);
@@ -434,7 +446,7 @@ struct Ptr
 	bool busy, flag, b;
 	int pia;
 
-	FILE *fp;
+	int fd;
 };
 Ptr *makeptr(IOBus *bus);
 void ptr_setmotor(Ptr *ptr, int m);
@@ -454,9 +466,3 @@ struct Tty
 };
 Tty *maketty(IOBus *bus);
 void attachdevtty(Tty *tty, const char *path);
-
-
-
-// for debugging
-char *names[0700];
-char *ionames[010];
diff --git a/emu/pt.c b/emu/pt.c
index d253cae..502465b 100644
--- a/emu/pt.c
+++ b/emu/pt.c
@@ -1,10 +1,10 @@
 #include "pdp6.h"
 #include <string.h>
 #include <unistd.h>
+#include <fcntl.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h> 
-#include <pthread.h>    
 #include <poll.h>
 
 /* TODO? implement motor delays */
@@ -24,66 +24,61 @@ recalc_ptr_req(Ptr *ptr)
 /* We have to punch after DATAO SET has happened. But BUSY is set by
  * DATAO CLEAR. So we use waitdatao to record when SET has happened */
 
-static void*
-ptpthread(void *dev)
+static void
+ptpcycle(void *p)
 {
 	Ptp *ptp;
+	uchar c;
 
-	ptp = dev;
-	for(;;){
-		if(ptp->busy && ptp->waitdatao){
-			if(ptp->fp){
-				if(ptp->b)
-					putc((ptp->ptp & 077) | 0200, ptp->fp);
-				else
-					putc(ptp->ptp, ptp->fp);
-				fflush(ptp->fp);
-			}
-			ptp->busy = 0;
-			ptp->flag = 1;
-			recalc_ptp_req(ptp);
+	ptp = p;
+	if(ptp->busy && ptp->waitdatao){
+		if(ptp->fd >= 0){
+			if(ptp->b)
+				c = (ptp->ptp & 077) | 0200;
+			else
+				c = ptp->ptp;
+			write(ptp->fd, &c, 1);
 		}
+		ptp->busy = 0;
+		ptp->flag = 1;
+		recalc_ptp_req(ptp);
 	}
-	return nil;
 }
 
-static void*
-ptrthread(void *dev)
+static void
+ptrcycle(void *p)
 {
 	Ptr *ptr;
-	int c;
+	uchar c;
 
-	ptr = dev;
-	for(;;){
-		if(ptr->busy && ptr->motor_on){
-			// PTR CLR
-			ptr->sr = 0;
-			ptr->ptr = 0;
-	next:
-			if(ptr->fp)
-				c = getc(ptr->fp);
-			else
-				c = 0;
-			if(c == EOF)
-				c = 0;
-			if(!ptr->b || c & 0200){
-				// PTR STROBE
-				ptr->sr <<= 1;
-				ptr->ptr <<= 6;
-				ptr->sr |= 1;
-				ptr->ptr |= c & 077;
-				if(!ptr->b)
-					ptr->ptr |= c & 0300;
-			}
-			if(!ptr->b || ptr->sr & 040){
-				ptr->busy = 0;
-				ptr->flag = 1;
-			}else
-				goto next;
-			recalc_ptr_req(ptr);
-		}
+	ptr = p;
+	if(!ptr->busy || !ptr->motor_on)
+		return;
+
+	// PTR CLR
+	ptr->sr = 0;
+	ptr->ptr = 0;
+next:
+	if(ptr->fd >= 0 && hasinput(ptr->fd)){
+		if(read(ptr->fd, &c, 1) != 1)
+			c = 0;
+	}else
+		c = 0;
+	if(!ptr->b || c & 0200){
+		// PTR STROBE
+		ptr->sr <<= 1;
+		ptr->ptr <<= 6;
+		ptr->sr |= 1;
+		ptr->ptr |= c & 077;
+		if(!ptr->b)
+			ptr->ptr |= c & 0300;
 	}
-	return nil;
+	if(!ptr->b || ptr->sr & 040){
+		ptr->busy = 0;
+		ptr->flag = 1;
+	}else
+		goto next;
+	recalc_ptr_req(ptr);
 }
 
 static void
@@ -193,30 +188,35 @@ ptr_setmotor(Ptr *ptr, int m)
 Ptp*
 makeptp(IOBus *bus)
 {
-	pthread_t thread_id;
 	Ptp *ptp;
+	Thread th;
 
 	ptp = malloc(sizeof(Ptp));
 	memset(ptp, 0, sizeof(Ptp));
 	ptp->bus = bus;
 	bus->dev[PTP] = (Busdev){ ptp, wake_ptp, 0 };
-	pthread_create(&thread_id, nil, ptpthread, ptp);
 
-	ptp->fp = fopen("../code/ptp.out", "wb");
+	th = (Thread){ nil, ptpcycle, ptp, 1, 0 };
+	addthread(th);
+
+	ptp->fd = open("../code/ptp.out", O_WRONLY | O_CREAT, 0666);
 	return ptp;
 }
 
 Ptr*
 makeptr(IOBus *bus)
 {
-	pthread_t thread_id;
 	Ptr *ptr;
+	Thread th;
 
 	ptr = malloc(sizeof(Ptr));
 	memset(ptr, 0, sizeof(Ptr));
 	ptr->bus = bus;
 	bus->dev[PTR] = (Busdev){ ptr, wake_ptr, 0 };
-	pthread_create(&thread_id, nil, ptrthread, ptr);
 
-	ptr->fp = fopen("../code/test.rim", "rb");
+	th = (Thread){ nil, ptrcycle, ptr, 1, 0 };
+	addthread(th);
+
+	ptr->fd = open("../code/test.rim", O_RDONLY);
+	return ptr;
 }
diff --git a/emu/tty.c b/emu/tty.c
index 8acee2a..4a921b5 100644
--- a/emu/tty.c
+++ b/emu/tty.c
@@ -2,7 +2,6 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <termios.h>
-#include <pthread.h>
 #include <poll.h>
 
 static void
@@ -11,23 +10,23 @@ recalc_tty_req(Tty *tty)
 	setreq(tty->bus, TTY, tty->tto_flag || tty->tti_flag ? tty->pia : 0);
 }
 
-/* TODO: implement some kind of sleep if no tty is attached */
-static void*
-ttythread(void *dev)
+static void
+ttycycle(void *p)
 {
+	Tty *tty;
 	int n;
 	char c;
-	Tty *tty;
 
-	tty = dev;
-	for(;;){
-		while(tty->fd >= 0 && (n = read(tty->fd, &c, 1)) > 0){
-			tty->tti_busy = 1;
-			tty->tti = c|0200;
-			tty->tti_busy = 0;
-			tty->tti_flag = 1;
-			recalc_tty_req(tty);
-		}
+	tty = p;
+	if(tty->fd >= 0 && hasinput(tty->fd)){
+		tty->tti_busy = 1;
+		n = read(tty->fd, &c, 1);
+		tty->tti = c|0200;
+		tty->tti_busy = 0;
+		if(n < 0)
+			return;
+		tty->tti_flag = 1;
+		recalc_tty_req(tty);
 	}
 }
 
@@ -123,14 +122,17 @@ fail:
 Tty*
 maketty(IOBus *bus)
 {
-	pthread_t thread_id;
 	Tty *tty;
+	Thread th;
 
 	tty = malloc(sizeof(Tty));
 	memset(tty, 0, sizeof(Tty));
 	tty->fd = -1;
 	tty->bus = bus;
 	bus->dev[TTY] = (Busdev){ tty, wake_tty, 0 };
-	pthread_create(&thread_id, nil, ttythread, tty);
+
+	th = (Thread){ nil, ttycycle, tty, 1, 0 };
+	addthread(th);
+
 	return tty;
 }
diff --git a/tools/args.h b/tools/args.h
new file mode 100644
index 0000000..0e666c1
--- /dev/null
+++ b/tools/args.h
@@ -0,0 +1,24 @@
+extern char *argv0;
+#define USED(x) ((void)x)
+#define SET(x) ((x)=0)
+
+#define	ARGBEGIN	for((argv0||(argv0=*argv)),argv++,argc--;\
+			    argv[0] && argv[0][0]=='-' && argv[0][1];\
+			    argc--, argv++) {\
+				char *_args, *_argt;\
+				char _argc;\
+				_args = &argv[0][1];\
+				if(_args[0]=='-' && _args[1]==0){\
+					argc--; argv++; break;\
+				}\
+				_argc = 0;\
+				while(*_args && (_argc = *_args++))\
+				switch(_argc)
+#define	ARGEND		SET(_argt);USED(_argt);USED(_argc);USED(_args);}USED(argv);USED(argc);
+#define	ARGF()		(_argt=_args, _args=(char*)"",\
+				(*_argt? _argt: argv[1]? (argc--, *++argv): 0))
+#define	EARGF(x)	(_argt=_args, _args=(char*)"",\
+				(*_argt? _argt: argv[1]? (argc--, *++argv): ((x), abort(), (char*)0)))
+
+#define	ARGC()		_argc
+
diff --git a/tools/pdp6common.c b/tools/pdp6common.c
index b7d697a..8de7f3e 100644
--- a/tools/pdp6common.c
+++ b/tools/pdp6common.c
@@ -42,7 +42,6 @@ readw(FILE *fp)
 void
 writewbak(word w, FILE *fp)
 {
-	unsigned char c;
 	putc((w >> 29) & 0177, fp);
 	putc((w >> 22) & 0177, fp);
 	putc((w >> 15) & 0177, fp);
diff --git a/tools/pdp6common.h b/tools/pdp6common.h
index ddda1c6..d44f525 100644
--- a/tools/pdp6common.h
+++ b/tools/pdp6common.h
@@ -28,3 +28,6 @@ int issixbit(char c);
 word sixbit(const char *s);
 void unsixbit(word sx, char *s);
 char *disasm(word w);
+
+extern char *mnemonics[448];
+extern char *iomnemonics[8];