diff --git a/doc/notes.txt b/doc/notes.txt
index ba6d7c17..d50c51d9 100644
--- a/doc/notes.txt
+++ b/doc/notes.txt
@@ -113,7 +113,7 @@ TODO:
   - multidim arrays
   - optimize trace log w/ wasm buffer
   - yosys compatibility 
-
+  - randomize on reset? (https://www.xilinx.com/support/documentation/white_papers/wp272.pdf)
 - single-stepping vector games makes screen fade
 - break on stack overflow, illegal op, bad access, BRK, etc
   - show in scope instead?
diff --git a/presets/verilog/chardisplay.v b/presets/verilog/chardisplay.v
index 133bc07c..daf4813f 100644
--- a/presets/verilog/chardisplay.v
+++ b/presets/verilog/chardisplay.v
@@ -80,5 +80,5 @@ module test_ram1_top(clk, reset, hsync, vsync, rgb);
         ram_writeenable <= 0;
       end
     endcase
-      
+
 endmodule
diff --git a/presets/verilog/digits10.v b/presets/verilog/digits10.v
index f1ad4e27..0a1903e3 100644
--- a/presets/verilog/digits10.v
+++ b/presets/verilog/digits10.v
@@ -163,11 +163,9 @@ module digits10_array(digit, yofs, bits);
     bitarray[9][4] = 5'b11111;
 
     // clear unused array entries
-    /* TODO
     for (i = 10; i <= 15; i++)
       for (j = 0; j <= 4; j++) 
         bitarray[i][j] = 0; 
-        */
   end
 endmodule
 
diff --git a/src/common/hdl/hdlwasm.ts b/src/common/hdl/hdlwasm.ts
index cac71624..a696982b 100644
--- a/src/common/hdl/hdlwasm.ts
+++ b/src/common/hdl/hdlwasm.ts
@@ -111,6 +111,7 @@ interface StructRec {
     index: number;
     init: HDLBlock;
     constval: HDLConstant;
+    reset: boolean;
 }
 
 class Struct {
@@ -144,6 +145,7 @@ class Struct {
             offset: this.len,
             init: null,
             constval: null,
+            reset: false,
         }
         this.len += size;
         if (rec.name != null) this.vars[rec.name] = rec;
@@ -196,6 +198,7 @@ export class HDLModuleWASM implements HDLModuleRunner {
     traceEndOffset: number;
     trace: any;
 
+    randomizeOnReset: boolean = false;
     finished: boolean;
     stopped: boolean;
     resetStartTimeMsec : number;
@@ -211,7 +214,6 @@ export class HDLModuleWASM implements HDLModuleRunner {
 
     async init() {
         await this.genModule();
-        this.genInitData();
         this.enableTracing();
     }
 
@@ -220,6 +222,8 @@ export class HDLModuleWASM implements HDLModuleRunner {
         this.resetStartTimeMsec = new Date().getTime() - 1;
         this.finished = false;
         this.stopped = false;
+        this.clearMutableState();
+        this.setInitialValues();
         (this.instance.exports as any)._ctor_var_reset(GLOBALOFS);
         (this.instance.exports as any)._eval_initial(GLOBALOFS);
         for (var i=0; i<100; i++) {
@@ -258,6 +262,7 @@ export class HDLModuleWASM implements HDLModuleRunner {
         this.data8.set(state.o as Uint8Array);
     }
 
+    // get tree of global variables for debugging
     getGlobals() {
         var g = {};
         for (const [varname, vardef] of Object.entries(this.hdlmod.vardefs)) {
@@ -329,8 +334,10 @@ export class HDLModuleWASM implements HDLModuleRunner {
         // generate global variables
         var state = new Struct();
         this.globals = state;
+        // separate vars and constants
+        var vardefs = Object.values(this.hdlmod.vardefs).filter(vd => vd.constValue == null);
+        var constdefs = Object.values(this.hdlmod.vardefs).filter(vd => vd.constValue != null);
         // sort globals by output flag and size
-        var vardefs = Object.values(this.hdlmod.vardefs);
         function getVarDefSortKey(vdef: HDLVariableDef) {
             var val = getDataTypeSize(vdef.dtype); // sort by size
             if (!vdef.isOutput) val += 1000000; // outputs are first in list
@@ -353,8 +360,11 @@ export class HDLModuleWASM implements HDLModuleRunner {
         }
         state.alignTo(8);
         this.statebytes = state.len;
-        // followed by constant pool
+        // followed by constants and constant pool
         if (this.constpool) {
+            for (const vardef of Object.values(constdefs)) {
+                state.addVar(vardef);
+            }
             for (const vardef of Object.values(this.constpool.vardefs)) {
                 state.addVar(vardef);
             }
@@ -444,11 +454,22 @@ export class HDLModuleWASM implements HDLModuleRunner {
 
     private defineProperty(proxy, basefn: () => number, vref: StructRec) {
         var _this = this;
+        // precompute some things
+        var elsize = vref.type && getArrayElementSizeFromType(vref.type);
+        var eltype = vref.type;
+        while (eltype && isArrayType(eltype)) {
+            eltype = eltype.subtype;
+        }
+        var mask = -1; // set all bits
+        if (eltype && isLogicType(eltype) && eltype.left < 31) {
+            mask = (1 << (eltype.left+1)) - 1; // set partial bits
+        }
+        // define get/set on proxy object
         Object.defineProperty(proxy, vref.name, {
             get() {
                 let base = basefn();
                 if (vref.type && isArrayType(vref.type)) {
-                    var elsize = getArrayElementSizeFromType(vref.type);
+                    // TODO: can't mask unused bits in array
                     if (elsize == 1) {
                         return new Uint8Array(_this.databuf, base + vref.offset, vref.size);
                     } else if (elsize == 2) {
@@ -470,13 +491,13 @@ export class HDLModuleWASM implements HDLModuleRunner {
             set(value) {
                 var base = basefn();
                 if (vref.size == 1) {
-                    _this.data8[(base + vref.offset)] = value;
+                    _this.data8[(base + vref.offset)] = value & mask;
                     return true;
                 } else if (vref.size == 2) {
-                    _this.data16[(base + vref.offset) >> 1] = value;
+                    _this.data16[(base + vref.offset) >> 1] = value & mask;
                     return true;
                 } else if (vref.size == 4) {
-                    _this.data32[(base + vref.offset) >> 2] = value;
+                    _this.data32[(base + vref.offset) >> 2] = value & mask;
                     return true;
                 } else {
                     throw new HDLError(vref, `can't set property ${vref.name}`);
@@ -495,27 +516,46 @@ export class HDLModuleWASM implements HDLModuleRunner {
         return proxy;
     }
 
-    private genInitData() {
+    setInitialValues() {
         for (var rec of this.globals.locals) {
-            if (rec.init) {
-                var arr = this.state[rec.name];
-                if (!arr) throw new HDLError(rec, `no array to init`);
-                for (let i=0; i<rec.init.exprs.length; i++) {
-                    let e = rec.init.exprs[i];
-                    if (isArrayItem(e) && isConstExpr(e.expr)) {
-                        arr[e.index] = e.expr.cvalue;
-                    } else {
-                        throw new HDLError(e, `non-const expr in initarray (multidimensional arrays not supported)`);
-                    }
+            this.setInitialValue(rec);
+        }
+    }
+
+    private setInitialValue(rec: StructRec) {
+        var arr = this.state[rec.name];
+        if (rec.init) {
+            if (!arr) throw new HDLError(rec, `no array to init`);
+            for (let i=0; i<rec.init.exprs.length; i++) {
+                let e = rec.init.exprs[i];
+                if (isArrayItem(e) && isConstExpr(e.expr)) {
+                    arr[e.index] = e.expr.cvalue;
+                } else {
+                    throw new HDLError(e, `non-const expr in initarray (multidimensional arrays not supported)`);
                 }
-                //console.log(rec.name, rec.type, arr);
             }
-            if (rec.constval) {
-                this.state[rec.name] = rec.constval.cvalue || rec.constval.bigvalue;
+            //console.log(rec.name, rec.type, arr);
+        } else if (rec.constval) {
+            this.state[rec.name] = rec.constval.cvalue || rec.constval.bigvalue;
+        } else if (rec.type && rec.reset && this.randomizeOnReset) {
+            if (isLogicType(rec.type) && typeof arr === 'number') {
+                this.state[rec.name] = Math.random() * 4294967296; // don't need to mask
+            } else if (isArrayType(rec.type) && isLogicType(rec.type.subtype)) {
+                // array types are't mask-protected yet
+                var mask = (1 << (rec.type.subtype.left + 1)) - 1;
+                for (var i=0; i<arr.length; i++) {
+                    arr[i] = (Math.random() * 4294967296) & mask;
+                }
+            } else {
+                console.log(`could not reset ${rec.name}`)
             }
         }
     }
 
+    clearMutableState() {
+        this.data32.fill(0, 0, this.statebytes >> 2);
+    }   
+
     private addHelperFunctions() {
         this.addCopyTraceRecFunction();
         this.addEvalFunction();
@@ -979,6 +1019,11 @@ export class HDLModuleWASM implements HDLModuleRunner {
     }
 
     _creset2wasm(e: HDLUnop, opts:Options) {
+        if (isVarRef(e.left)) {
+            var glob = this.globals.lookup(e.left.refname);
+            // TOOD: must be better way to tell non-randomize values
+            if (glob && !glob.name.startsWith("__")) glob.reset = true;
+        }
         // TODO return this.e2w(e.left, opts);
         return this.bmod.nop();
     }
diff --git a/src/ide/embedui.ts b/src/ide/embedui.ts
index ebd1ce3a..f5fea861 100644
--- a/src/ide/embedui.ts
+++ b/src/ide/embedui.ts
@@ -66,13 +66,13 @@ function addPageFocusHandlers() {
   });
 }
 
-function startROM(title, rom) {
+async function startROM(title, rom) {
   if (!rom ) {
     alert("No ROM found.");
     return;
   }
   console.log(rom.length + ' bytes');
-  platform.loadROM(title, rom);
+  await platform.loadROM(title, rom);
   platform.resume();
 }
 
diff --git a/src/ide/ui.ts b/src/ide/ui.ts
index 88e47ce7..111b7551 100644
--- a/src/ide/ui.ts
+++ b/src/ide/ui.ts
@@ -1156,7 +1156,7 @@ function measureBuildTime() {
   //gaEvent('build', platform_id);
 }
 
-function setCompileOutput(data: WorkerResult) {
+async function setCompileOutput(data: WorkerResult) {
   // errors? mark them in editor
   if (data && data.errors && data.errors.length > 0) {
     toolbar.addClass("has-errors");
@@ -1178,7 +1178,7 @@ function setCompileOutput(data: WorkerResult) {
       try {
         clearBreakpoint(); // so we can replace memory (TODO: change toolbar btn)
         _resetRecording();
-        platform.loadROM(getCurrentPresetTitle(), rom); // TODO: should be async?
+        await platform.loadROM(getCurrentPresetTitle(), rom);
         current_output = rom;
         if (!userPaused) _resume();
         measureBuildTime();
diff --git a/src/platform/verilog.ts b/src/platform/verilog.ts
index 1062a369..3108d75d 100644
--- a/src/platform/verilog.ts
+++ b/src/platform/verilog.ts
@@ -190,7 +190,7 @@ var VerilogPlatform = function(mainElement, options) {
     await loadScript('./gen/common/hdl/hdltypes.js');
     await loadScript('./gen/common/hdl/hdlruntime.js');
     await loadScript('./gen/common/hdl/hdlwasm.js');
-    await loadScript('./lib/binaryen.js'); // TODO: path?
+    await loadScript('./lib/binaryen.js');
     video = new RasterVideo(mainElement,videoWidth,videoHeight,{overscan:true});
     video.create();
     poller = setKeyboardFromMap(video, switches, VERILOG_KEYCODE_MAP, (o,key,code,flags) => {
@@ -275,7 +275,7 @@ var VerilogPlatform = function(mainElement, options) {
     }
     // paint into frame, synched with vsync if full speed
     var trace = this.isScopeVisible();
-    this.updateVideoFrameCycles(cyclesPerFrame * fps/60 + 1, sync, trace);
+    this.updateVideoFrameCycles(Math.ceil(cyclesPerFrame * fps/60), sync, trace);
     if (fps < 0.25) {
       idata[frameidx] = -1;
     }
@@ -431,9 +431,7 @@ var VerilogPlatform = function(mainElement, options) {
     if (scanlineCycles <= 0) throw new Error(`scanlineCycles must be > 0`);
     var maxLineCycles = 1009; // prime number so we eventually sync up
     var nextlineCycles = scanlineCycles || maxLineCycles;
-    // TODO: we can go faster if no paddle/sound
     frameidx = 0;
-    var wasvsync = false;
     // audio feed
     function spkr() { if (useAudio) audio.feedSample(tmod.trace.spkr, 1); }
     // iterate through a frame of scanlines + room for vsync
@@ -446,7 +444,6 @@ var VerilogPlatform = function(mainElement, options) {
       if (nextlineCycles > 0) {
         top.tick2(nextlineCycles);
       }
-      // TODO: this has to be done more quickly
       resetKbdStrobe();
       // convert trace buffer to video/audio
       var n = 0;
@@ -496,10 +493,12 @@ var VerilogPlatform = function(mainElement, options) {
       tmod.resetTrace();
       // exit when vsync starts and then stops
       if (tmod.trace.vsync) {
-        wasvsync = true;
+        framevsync = true;
         top.state.hpaddle = 0;
         top.state.vpaddle = 0;
-      } else if (wasvsync) {
+        framex = framey = frameidx = 0;
+      } else if (framevsync) {
+        framevsync = false;
         break;
       }
     }
@@ -577,7 +576,6 @@ var VerilogPlatform = function(mainElement, options) {
     }
   }
 
-  // TODO: can this be async?
   async loadROM(title:string, output:any) {
     var unit = output as HDLUnit;
     var topmod = unit.modules['TOP'];
@@ -589,7 +587,6 @@ var VerilogPlatform = function(mainElement, options) {
         var _top = new topcons(topmod, unit.modules['@CONST-POOL@']);
         _top.getFileData = (path) => current_project.filedata[path]; // external file provider
         await _top.init();
-        _top.powercycle();
         this.dispose();
         top = _top;
         // create signal array
@@ -610,6 +607,9 @@ var VerilogPlatform = function(mainElement, options) {
         trace_signals = trace_signals.filter((v) => { return !v.label.startsWith("__V"); }); // remove __Vclklast etc
         trace_index = 0;
         // reset
+        if (top instanceof HDLModuleWASM) {
+          top.randomizeOnReset = true;
+        }
         this.poweron();
         // query output signals -- video or not?
         this.hasvideo = top.state.vsync != null && top.state.hsync != null && top.state.rgb != null;
@@ -702,7 +702,7 @@ var VerilogPlatform = function(mainElement, options) {
   }
   reset() {
     if (!top) return;
-    //top.reset(); // to avoid clobbering user inputs
+    // TODO: how do we avoid clobbering user-modified signals?
     doreset();
     trace_index = 0;
     if (trace_buffer) trace_buffer.fill(0);
@@ -754,7 +754,6 @@ var VerilogPlatform = function(mainElement, options) {
     }
   }
 
-  // TODO: bind() a function to avoid depot?
   saveState() {
     return {o: top && top.saveState()};
   }
@@ -782,7 +781,6 @@ var VerilogPlatform = function(mainElement, options) {
     keycode = state.keycode;
   }
   getDownloadFile() {
-    // TODO: WASM code too?
     if (top instanceof HDLModuleJS) {
       return {
         extension:".js", 
@@ -795,6 +793,9 @@ var VerilogPlatform = function(mainElement, options) {
       };
     }
   }
+  getHDLModuleRunner() {
+    return top;
+  }
 
  } // end of inner class
  return new _VerilogPlatform();  
diff --git a/test/cli/testverilog.js b/test/cli/testverilog.js
index b4ad7a57..d58a2725 100644
--- a/test/cli/testverilog.js
+++ b/test/cli/testverilog.js
@@ -28,6 +28,8 @@ async function loadPlatform(msg) {
     //console.log(msg.output.ports);
     //console.log(msg.output.signals);
     await platform.loadROM("ROM", msg.output);
+    platform.getHDLModuleRunner().randomizeOnReset = false;
+    platform.getHDLModuleRunner().powercycle();
     //await platform.loadROM("ROM", msg.output);
     for (var i=0; i<100000 && !platform.isBlocked(); i++) {
       platform.tick();