diff --git a/src/platform/sms.ts b/src/platform/sms.ts
index 94d23706..71b0f809 100644
--- a/src/platform/sms.ts
+++ b/src/platform/sms.ts
@@ -10,6 +10,7 @@ import { ColecoVision_PRESETS } from "./coleco";
 // http://www.smspower.org/Development/Index
 // http://www.smspower.org/uploads/Development/sg1000.txt
 // http://www.smspower.org/uploads/Development/richard.txt
+// http://www.smspower.org/uploads/Development/msvdp-20021112.txt
 
 // TODO: merge w/ coleco
 export var SG1000_PRESETS = [
@@ -68,8 +69,8 @@ class SG1000Platform extends BaseZ80Platform {
   inputs = new Uint8Array(4);
   mainElement : HTMLElement;
 
-  isSMS = false; // TODO: remove
   currentScanline : number;
+  startLineTstates : number;
   
   constructor(mainElement : HTMLElement) {
     super();
@@ -96,13 +97,19 @@ class SG1000Platform extends BaseZ80Platform {
     };
   }
   
+  getVCounter() : number { return 0; }
+  getHCounter() : number { return 0; }
+  setMemoryControl(v:number) { }
+  setIOPortControl(v:number) { }
+  
   newIOBus() {
     return {
       read: (addr:number) => {
         addr &= 0xff;
         //console.log('IO read', hex(addr,4));
         switch (addr & 0xc1) {
-          case 0x40: return this.isSMS ? this.currentScanline : 0;
+          case 0x40: return this.getVCounter();
+          case 0x41: return this.getHCounter();
           case 0x80: return this.vdp.readData();
           case 0x81: return this.vdp.readStatus();
           case 0xc0: return this.inputs[0] ^ 0xff;
@@ -115,10 +122,12 @@ class SG1000Platform extends BaseZ80Platform {
         val &= 0xff;
         //console.log('IO write', hex(addr,4), hex(val,2));
         switch (addr & 0xc1) {
-          case 0x80: return this.vdp.writeData(val);
-          case 0x81: return this.vdp.writeAddress(val);
+          case 0x00: return this.setMemoryControl(val);
+          case 0x01: return this.setIOPortControl(val);
           case 0x40:
           case 0x41: return this.psg.setData(val);
+          case 0x80: return this.vdp.writeData(val);
+          case 0x81: return this.vdp.writeAddress(val);
         }
       }
     };
@@ -159,6 +168,7 @@ class SG1000Platform extends BaseZ80Platform {
   advance(novideo : boolean) {
     for (var sl=0; sl<this.numTotalScanlines; sl++) {
       this.currentScanline = sl;
+      this.startLineTstates = this.cpu.getTstates();
       this.runCPU(this.cpu, this.cpuCyclesPerLine);
       this.vdp.drawScanline(sl);
     }
@@ -232,22 +242,43 @@ class SG1000Platform extends BaseZ80Platform {
 
 class SMSPlatform extends SG1000Platform {
 
-  isSMS = true;
-  
   cartram : RAM = new RAM(0);
   pagingRegisters = new Uint8Array(4);
   romPageMask : number;
+  // TODO: add to state
+  latchedHCounter = 0;
+  ioControlFlags = 0;
   // TODO: hide bottom scanlines
   
   reset() {
     super.reset();
     this.pagingRegisters.set([0,0,1,2]);
   }
-  
+
   newVDP(frameData, cru, flicker) {
     return new SMSVDP(frameData, cru, flicker);
   }
   
+  getVCounter() {
+    var y = this.currentScanline;
+    return (y <= 0xda) ? (y) : (y - 6);
+  }
+  getHCounter() {
+    return this.latchedHCounter;
+  }
+  computeHCounter() {
+    var t0 = this.startLineTstates;
+    var t1 = this.cpu.getTstates();
+    return (t1-t0) & 0xff; // TODO
+  }
+  setIOPortControl(v:number) {
+    if ((v ^ this.ioControlFlags) & 0xa0) { // either joystick TH pin
+      this.latchedHCounter = this.computeHCounter();
+      //console.log("H:"+hex(this.latchedHCounter)+" V:"+hex(this.getVCounter()));
+    }
+    this.ioControlFlags = v;
+  }
+  
   newRAM() { return new RAM(0x2000); }
   
   getPagedROM(a:number, reg:number) {
diff --git a/src/video/tms9918a.ts b/src/video/tms9918a.ts
index 69fb7ab8..60348c24 100644
--- a/src/video/tms9918a.ts
+++ b/src/video/tms9918a.ts
@@ -43,8 +43,8 @@ export class TMS9918A {
   latch : boolean;
   prefetchByte : number;
 
-  displayOn = null;
-  interruptsOn = null;
+  displayOn : boolean = false;
+  interruptsOn : boolean = false;
   screenMode : number;
   bitmapMode : boolean;
   textMode : boolean;
@@ -493,6 +493,7 @@ export class TMS9918A {
 
     writeData(i:number) {
         this.ram[this.addressRegister++] = i;
+        this.prefetchByte = i;
         this.addressRegister &= this.ramMask;
         this.latch = false;
         this.redrawRequired = true;
@@ -674,6 +675,9 @@ export class SMSVDP extends TMS9918A {
     cpalette = new Uint32Array(32); // color RAM (RGBA)
     registers = new Uint8Array(16); // 8 more registers (actually only 5)
     vramUntwiddled = new Uint8Array(0x8000);
+    numVisibleLines = 192;
+    lineCounter = 0; // TODO: state
+    lineInterruptPending = false; // TODO: state
 
     reset() {
         super.reset();
@@ -682,6 +686,10 @@ export class SMSVDP extends TMS9918A {
         this.cpalette.fill(0);
         this.vramUntwiddled.fill(0);        
     }
+    readStatus() {
+        this.lineInterruptPending = false;
+        return super.readStatus();
+    }
     updateMode(reg0:number, reg1:number) {
         if (reg0 & 0x04) {
             this.screenMode = TMS9918A_Mode.MODE4;
@@ -713,6 +721,7 @@ export class SMSVDP extends TMS9918A {
             var palindex = this.addressRegister++ & (this.cram.length-1);
             this.cram[palindex] = i;
             this.cpalette[palindex] = RGBA((i&3)<<6, ((i>>2)&3)<<6, ((i>>4)&3)<<6);
+            this.prefetchByte = i;
             this.addressRegister &= this.ramMask;
             this.redrawRequired = true;
         } else {
@@ -722,16 +731,6 @@ export class SMSVDP extends TMS9918A {
         }
         this.latch = false;
     }
-    readData() : number {
-        if (this.writeToCRAM) {
-            var palindex = this.addressRegister++ & (this.cram.length-1);
-            this.addressRegister &= this.ramMask;
-            return this.cram[palindex];
-        } else {
-            return super.readData();
-        }
-    }
-
     writeTwiddled(vdp_addr:number, val:number) {
         var planarBase = vdp_addr & 0x3ffc;
         var twiddledBase = planarBase * 2;
@@ -934,25 +933,24 @@ export class SMSVDP extends TMS9918A {
         count = count | 0;
         const borderIndex = 16 + (this.registers[7] & 0xf);
         const borderRGB = this.cpalette[borderIndex];
-        for (var i = 0; i < count; i++)
-            this.fb32[lineAddr + i] = borderRGB;
+        this.fb32.fill(borderRGB, lineAddr, lineAddr+count);
     }
 
     rasterize_line(line:number) {
+        line |= 0;
         var vdp_regs = this.registers;
-        var drawHeight = 192; // TODO?
-        var hBorder = (this.width - 256) >> 1;
-        var vBorder = (this.height - 192) >> 1; // TODO?
-        line = (line - vBorder*0) | 0; // TODO?
-        const startAddr = (line * this.width) | 0;
+        var drawWidth = 256;
+        var drawHeight = this.numVisibleLines; // TODO?
+        var hBorder = (this.width - drawWidth) >> 1;
+        var vBorder = (this.height - drawHeight) >> 1; // TODO?
+        const startAddr = ((line + vBorder) * this.width) | 0;
         const lineAddr = (startAddr + hBorder) | 0;
-        if (!(line >= 0 && line < 224 && this.displayOn)) {
-            this.border_clear(startAddr, this.width);
-        }
-        else if ((vdp_regs[1] & 64) === 0) {
-            this.border_clear(startAddr, this.width);
-        }
-        else {
+        if (!this.displayOn || line < 0 || line >= drawHeight) {
+            if (line < this.height)
+                this.border_clear(startAddr, this.width);
+            else if (line >= 262-vBorder)
+                this.border_clear((line-262+vBorder)*this.width, this.width);
+        } else {
             var effectiveLine = line + vdp_regs[9];
             if (effectiveLine >= 224) {
                 effectiveLine -= 224;
@@ -973,12 +971,29 @@ export class SMSVDP extends TMS9918A {
                 this.border_clear(lineAddr, 8);
             }
         }
+        // frame interrupts
         if (line == drawHeight) {
             this.statusRegister |= 0x80;
             if (this.interruptsOn) {
                 this.cru.setVDPInterrupt(true);
             }
         }
+        // line interrupts
+        if (line <= drawHeight) {
+            if (this.lineCounter > 0) {
+                this.lineCounter--;
+            } else {
+                this.lineCounter = this.registers[0xa];
+                this.lineInterruptPending = true;
+            }
+        } else {
+            this.lineCounter = this.registers[0xa];
+        }
+        if (this.lineInterruptPending) {
+            if (this.registers[0] & 0x10) {
+                // TODO this.cru.setVDPInterrupt(true);
+            }
+        }
     }
 
     getDebugTables() {