diff --git a/6.out b/6.out
new file mode 100755
index 0000000..1340528
Binary files /dev/null and b/6.out differ
diff --git a/a.out b/a.out
new file mode 100644
index 0000000..9ccd6a7
Binary files /dev/null and b/a.out differ
diff --git a/cpu.6 b/cpu.6
new file mode 100644
index 0000000..1629dc2
Binary files /dev/null and b/cpu.6 differ
diff --git a/cpu.c b/cpu.c
index 9d61b46..4938f27 100644
--- a/cpu.c
+++ b/cpu.c
@@ -3,32 +3,31 @@
 #include "dat.h"
 #include "fns.h"
 
-u8int	*mem;
 u8int	rA, rS, rX, rY, rP;
 u16int	pc;
 
 int	irq, nmi;
 
-static void
+void
 push8(u8int v)
 {
 	memwrite(0x100 | rS--, v);
 }
 
-static void
+void
 push16(u16int v)
 {
 	memwrite(0x100 | rS--, v >> 8);
 	memwrite(0x100 | rS--, v);
 }
 
-static u8int
+u8int
 pop8(void)
 {
 	return memread(0x100 | ++rS);
 }
 
-static u16int
+u16int
 pop16(void)
 {
 	u16int v;
@@ -38,13 +37,13 @@ pop16(void)
 	return v;
 }
 
-static u8int
+u8int
 fetch8(void)
 {
 	return memread(pc++);
 }
 
-static u16int
+u16int
 fetch16(void)
 {
 	u16int r;
@@ -54,7 +53,7 @@ fetch16(void)
 	return r;
 }
 
-static void
+void
 nz(u8int v)
 {
 	rP &= ~(Negative | Zero);
@@ -64,7 +63,7 @@ nz(u8int v)
 		rP |= Zero;
 }
 
-static void
+void
 adc(u8int d)
 {
 	int r;
@@ -78,7 +77,7 @@ adc(u8int d)
 	if(rA == 0) rP |= Zero;
 }
 
-static void
+void
 sbc(u8int d)
 {
 	int r;
@@ -92,7 +91,7 @@ sbc(u8int d)
 	if(rA & 0x80) rP |= Negative;
 }
 
-static void
+void
 asl(u16int a)
 {
 	u8int v;
@@ -109,7 +108,7 @@ asl(u16int a)
 	memwrite(a, v);
 }
 
-static void
+void
 lsr(u16int a)
 {
 	u8int v;
@@ -123,7 +122,7 @@ lsr(u16int a)
 	memwrite(a, v);
 }
 
-static void
+void
 rol(u16int a)
 {
 	u8int v, b;
@@ -138,7 +137,7 @@ rol(u16int a)
 	memwrite(a, v);
 }
 
-static void
+void
 ror(u16int a)
 {
 	u8int v, b;
@@ -153,7 +152,7 @@ ror(u16int a)
 	memwrite(a, v);
 }
 
-static void
+void
 cmp(u8int A, u8int B)
 {
 	rP &= ~(Negative | Zero | Carry);
@@ -162,7 +161,7 @@ cmp(u8int A, u8int B)
 	if((A - B) & 0x80) rP |= Negative;
 }
 
-static void
+void
 inc(u16int a)
 {
 	u8int v;
@@ -173,7 +172,7 @@ inc(u16int a)
 	memwrite(a, v);
 }
 
-static void
+void
 dec(u16int a)
 {
 	u8int v;
@@ -184,7 +183,7 @@ dec(u16int a)
 	memwrite(a, v);
 }
 
-static int
+int
 branch(void)
 {
 	s8int t;
@@ -200,7 +199,7 @@ branch(void)
 	return 3;
 }
 
-static u16int
+u16int
 aindX(void)
 {
 	u8int r;
@@ -212,7 +211,7 @@ aindX(void)
 	return b;
 }
 
-static u16int
+u16int
 aindY(int *p)
 {
 	u8int r;
@@ -225,7 +224,7 @@ aindY(int *p)
 	return b;
 }
 
-static void
+void
 interrupt(int nmi, int brk)
 {
 	push16(pc);
diff --git a/fns.h b/fns.h
index 591f2ae..3d48ad8 100644
--- a/fns.h
+++ b/fns.h
@@ -1,5 +1,5 @@
-int	step(void);
-u8int	memread(u16int);
-void	memwrite(u16int, u8int);
+extern int	step(void);
+extern u8int	memread(u16int);
+extern void	memwrite(u16int, u8int);
 
-static u16int	fetch16(void);
+extern u16int	fetch16(void);
diff --git a/main.6 b/main.6
new file mode 100644
index 0000000..b599103
Binary files /dev/null and b/main.6 differ
diff --git a/main.c b/main.c
index 9bab683..810b8f9 100644
--- a/main.c
+++ b/main.c
@@ -6,7 +6,7 @@
 void
 usage(void)
 {
-	fprint(2, "usage: %s [ -s target speed ] [ prog ]\n", argv0);
+	fprint(2, "usage: %s [ -s target cycle length ] prog\n", argv0);
 	exits("usage");
 }
 
@@ -23,14 +23,14 @@ openprog(char *f)
 		sysfatal("cannot open program: %r");
 	d = dirfstat(fd);
 	if(d->length > 0xFF00)
-		sysfatal("program too big: size does not permit whole zp access");
+		sysfatal("program too big: cannot be bigger than $ff00");
 	romptr = mem+32768;
-	romptr = romptr + 32768 - d->length;
-	s = romptr-mem;
+	romptr += 32768 - d->length;
+	s = mem+65536-romptr;
 	free(d);
 	n = read(fd, romptr, s);
 	if(n != s)
-		fprint(2, "tried to read %uld bytes, got %ld bytes\n", s, n);
+		fprint(2, "tried to read %ulld bytes, got %ld bytes\n", s, n);
 	close(fd);
 }
 
@@ -42,6 +42,9 @@ main(int argc, char **argv)
 	vlong target;
 
 	target = 1000;
+	mem = malloc(0x10000);
+	if(mem == nil)
+		sysfatal("bad malloc for mem");
 	ARGBEGIN{
 	case 's':
 		target = atoll(EARGF(usage()));
@@ -50,6 +53,8 @@ main(int argc, char **argv)
 		usage();
 		break;
 	}ARGEND
+	if(!argc)
+		usage();
 	openprog(*argv);
 	rP = 0x34;
 	pc = 0xFFFC;
diff --git a/mem.6 b/mem.6
new file mode 100644
index 0000000..bd5c8b8
Binary files /dev/null and b/mem.6 differ
diff --git a/mem.c b/mem.c
index acca583..0106299 100644
--- a/mem.c
+++ b/mem.c
@@ -3,6 +3,9 @@
 #include "dat.h"
 #include "fns.h"
 
+u8int	*mem;
+u8int	*romptr;
+
 u8int
 memread(u16int a)
 {
@@ -12,6 +15,6 @@ memread(u16int a)
 void
 memwrite(u16int a, u8int v)
 {
-	if(a < romptr)
+	if((void*)a < romptr)
 		mem[a] = v;
 }
diff --git a/mkfile b/mkfile
index 3119eb5..2b5dafa 100755
--- a/mkfile
+++ b/mkfile
@@ -3,15 +3,9 @@
 BIN=/$objtype/bin
 
 TARG=scemu
-OFILES=scemu.$O
+OFILES=main.$O cpu.$O mem.$O
 UPDATE=mkfile prog.s ${OFILES:%.$O=%.c}
 
-default:V:	$O.out a.out
+default:V:	$O.out
 
 </sys/src/cmd/mkone
-
-a.out:	prog.s
-	vasm -Fbin -dotdir prog.s
-
-clean:
-	rm -f a.out [$OS].out *.[$OS]
diff --git a/test.s b/test.s
new file mode 100644
index 0000000..4b3a2a8
--- /dev/null
+++ b/test.s
@@ -0,0 +1,11 @@
+	.org $ff00
+reset:
+	lda #'\'
+	sta $7000
+loop:
+	ror
+	jmp loop
+	.org $fffa
+	.word reset
+	.word reset
+	.word reset