diff --git a/presets/c64/common.c b/presets/c64/common.c
index a8810a99..d2b6a166 100644
--- a/presets/c64/common.c
+++ b/presets/c64/common.c
@@ -5,6 +5,10 @@ void raster_wait(byte line) {
   while (VIC.rasterline < line) ;
 }
 
+void wait_vblank(void) {
+  raster_wait(250);
+}
+
 static byte VIC_BANK_PAGE[4] = {
   0xc0, 0x80, 0x40, 0x00
 };
@@ -24,3 +28,13 @@ char __fastcall__ poll_keyboard() {
 }
 #endif
 
+void set_raster_irq(char scanline) {
+  // deactivate CIA interrupts (keyboard, etc)
+  CIA1.icr = 0x7f;
+  // set raster line for interrupt
+  VIC.ctrl1 &= 0x7f; // clear raster line bit 8
+  VIC.rasterline = scanline;
+  // activate VIC raster interrupts
+  VIC.imr = 1;
+}
+
diff --git a/presets/c64/common.h b/presets/c64/common.h
index 663ebfe8..1d4a7dd1 100644
--- a/presets/c64/common.h
+++ b/presets/c64/common.h
@@ -80,10 +80,10 @@ typedef enum { false, true } bool; // boolean
 
 // set scrolling registers
 #define SET_SCROLL_Y(_y) \
-  VIC.ctrl1 = (VIC.ctrl1 & 0xf8) | (_y);
+  VIC.ctrl1 = (VIC.ctrl1 & 0xf8) | (_y & 7);
 
 #define SET_SCROLL_X(_x) \
-  VIC.ctrl2 = (VIC.ctrl2 & 0xf8) | (_x);
+  VIC.ctrl2 = (VIC.ctrl2 & 0xf8) | (_x & 7);
 
 
 // enable RAM from 0xa000-0xffff, disable interrupts
@@ -102,6 +102,9 @@ typedef enum { false, true } bool; // boolean
 // wait until specific raster line
 void raster_wait(byte line);
 
+// wait until end of frame
+void wait_vblank();
+
 // get current VIC bank start address
 char* get_vic_bank_start();
 
@@ -132,4 +135,9 @@ inline void waitvsync() {
 }
 #endif
 
+// for use with set_irq()
+// sets up the VIC to send raster interrupts
+// and disables CIA interrupts
+void set_raster_irq(char scanline);
+
 #endif
diff --git a/presets/c64/scroll1.c b/presets/c64/scroll1.c
index c4b62f4f..976a1cee 100644
--- a/presets/c64/scroll1.c
+++ b/presets/c64/scroll1.c
@@ -63,8 +63,8 @@ void main(void) {
   
   // infinite loop
   while (1) {
-    // wait for vsync
-    waitvsync();
+    // wait for end of frame
+    wait_vblank();
     // scroll one pixel to the left
     // and move screen memory every 8 pixels
     scroll_one_pixel_left();
diff --git a/presets/c64/scroll2.c b/presets/c64/scroll2.c
index c77f5b0b..bc26fc00 100644
--- a/presets/c64/scroll2.c
+++ b/presets/c64/scroll2.c
@@ -23,8 +23,8 @@ void scroll_one_pixel_left() {
   src = scrnbuf[visbuf] + (scroll_x & 7) * 128;
   // destination = hidden buffer
   dst = scrnbuf[visbuf ^ 1] + (scroll_x & 7) * 128;
-  // wait for vsync
-  waitvsync();
+  // wait for end of frame
+  wait_vblank();
   // scroll hidden buffer
   memcpy(dst, src+1, 128);
   // every 8 pixels, switch visible and hidden buffers
diff --git a/presets/c64/scroll3.c b/presets/c64/scroll3.c
index c074c58a..902a0001 100644
--- a/presets/c64/scroll3.c
+++ b/presets/c64/scroll3.c
@@ -17,8 +17,8 @@ void scroll_update_regs() {
 void scroll_swap() {
   // swap hidden and visible buffers
   hidbuf ^= 1;
-  // wait for vblank and update registers
-  waitvsync();
+  // wait for end of frame and update registers
+  wait_vblank();
   scroll_update_regs();
   SET_VIC_SCREEN(hidbuf ? 0x8000 : 0x8400);
 }
diff --git a/presets/c64/scroll4.c b/presets/c64/scroll4.c
index efbc583e..7e32a7c9 100644
--- a/presets/c64/scroll4.c
+++ b/presets/c64/scroll4.c
@@ -83,8 +83,8 @@ void main(void) {
     // animate sprite in shadow sprite ram
     sprite_draw(0, n++, 70, 192);
     sprite_draw(0, 172, 145, 192);
-    // wait for vblank
-    waitvsync();
+    // wait for end of frame
+    wait_vblank();
     // update scroll registers
     // and swap screens if we must
     scroll_update();
diff --git a/presets/c64/scroll5.c b/presets/c64/scroll5.c
index 7fc744d7..e81efc49 100644
--- a/presets/c64/scroll5.c
+++ b/presets/c64/scroll5.c
@@ -118,7 +118,7 @@ void main(void) {
     // animate sprite in shadow sprite ram
     update_player();
     // wait for end of frame
-    waitvsync();
+    wait_vblank();
     // then update sprite registers
     sprite_update(visbuf);
     // update scroll registers
diff --git a/presets/c64/test_setirq.c b/presets/c64/test_setirq.c
index 34064b4a..a82e46a3 100644
--- a/presets/c64/test_setirq.c
+++ b/presets/c64/test_setirq.c
@@ -34,16 +34,6 @@ char interrupt_handler() {
   return IRQ_HANDLED;
 }
 
-void set_frame_irq(char scanline) {
-  // deactivate CIA interrupts (keyboard, etc)
-  CIA1.icr = 0x7f;
-  // set raster line for interrupt
-  VIC.ctrl1 &= 0x7f; // clear raster line bit 8
-  VIC.rasterline = scanline;
-  // activate VIC raster interrupts
-  VIC.imr = 1;
-}
-
 void main(void) {
   clrscr();
   printf("\nHello World!\n");
@@ -52,7 +42,7 @@ void main(void) {
   set_irq(interrupt_handler, (void*)0x9f00, 0x100);
   
   // disable CIA interrupt, activate VIC interrupt
-  set_frame_irq(255);
+  set_raster_irq(255);
 
   while (1) {
     printf("%d ", VIC.rasterline);
diff --git a/src/test/testwasishim.ts b/src/test/testwasishim.ts
index a7f15f3b..698c4ac2 100644
--- a/src/test/testwasishim.ts
+++ b/src/test/testwasishim.ts
@@ -3,7 +3,7 @@ import { WASIRunner } from "../common/wasi/wasishim";
 import * as fs from "fs";
 
 async function loadWASM(filename: string) {
-    const wasmdata = fs.readFileSync(`./wasi/${filename}.wasm`);
+    const wasmdata = fs.readFileSync(`./src/worker/wasm/${filename}.wasm`);
     let shim = new WASIRunner();
     await shim.loadAsync(wasmdata);
     return shim;
@@ -12,8 +12,8 @@ async function loadWASM(filename: string) {
 async function loadDASM() {
     return loadWASM('dasm-wasisdk');
 }
-async function loadCC2600() {
-    return loadWASM('cc2600');
+async function loadCC7800() {
+    return loadWASM('cc7800');
 }
 
 describe('test WASI DASM', function () {
@@ -66,11 +66,14 @@ describe('test WASI DASM', function () {
     });
 });
 
-describe('test WASI cc2600', function () {
-    it('cc2600 help', async function () {
-        let shim = await loadCC2600();
-        shim.setArgs(["cc2600", '-h']);
+describe('test WASI cc7800', function () {
+    it('cc7800 help', async function () {
+        let shim = await loadCC7800();
+        shim.setArgs(["cc7800", '-h']);
         let errno = shim.run();
         assert.strictEqual(errno, 0);
+        const stdout = shim.fds[1].getBytesAsString();
+        console.log(stdout);
+        assert.ok(stdout.indexOf('Usage: cc7800') >= 0);
     });
 });
diff --git a/src/worker/wasm/dasm-wasisdk.wasm b/src/worker/wasm/dasm-wasisdk.wasm
new file mode 100755
index 00000000..7284d2ba
Binary files /dev/null and b/src/worker/wasm/dasm-wasisdk.wasm differ