2 files changed, 37 insertions, 1 deletions
diff --git a/demo/src/cpu-performance.ts b/demo/src/cpu-performance.ts
new file mode 100644
index 0000000..f61d038
--- /dev/null
+++ b/demo/src/cpu-performance.ts
@@ -0,0 +1,33 @@
+import { ICPU } from 'avr8js';
+
+export class CPUPerformance {
+  private prevTime = 0;
+  private prevCycles = 0;
+  private samples = new Float32Array(64);
+  private sampleIndex = 0;
+
+  constructor(private cpu: ICPU, private MHZ: number) {}
+
+  reset() {
+    this.prevTime = 0;
+    this.prevCycles = 0;
+    this.sampleIndex = 0;
+  }
+
+  update() {
+    if (this.prevTime) {
+      const delta = performance.now() - this.prevTime;
+      const deltaCycles = this.cpu.cycles - this.prevCycles;
+      const deltaCpuMillis = 1000 * (deltaCycles / this.MHZ);
+      const factor = deltaCpuMillis / delta;
+      if (!this.sampleIndex) {
+        this.samples.fill(factor);
+      }
+      this.samples[this.sampleIndex++ % this.samples.length] = factor;
+    }
+    this.prevCycles = this.cpu.cycles;
+    this.prevTime = performance.now();
+    const avg = this.samples.reduce((x, y) => x + y) / this.samples.length;
+    return avg;
+  }
+}
diff --git a/demo/src/index.ts b/demo/src/index.ts
index 7b6f9b1..a173f04 100644
--- a/demo/src/index.ts
+++ b/demo/src/index.ts
@@ -3,6 +3,7 @@ import { AVRRunner } from './execute';
 import { formatTime } from './format-time';
 import './index.css';
 import { LED } from './led';
+import { CPUPerformance } from './cpu-performance';
 
 let editor: any;
 const BLINK_CODE = `
@@ -68,9 +69,11 @@ function executeProgram(hex: string) {
   runner.usart.onByteTransmit = (value) => {
     serialOutputText.textContent += String.fromCharCode(value);
   };
+  const cpuPerf = new CPUPerformance(runner.cpu, MHZ);
   runner.execute((cpu) => {
     const time = formatTime(cpu.cycles / MHZ);
-    statusLabel.textContent = 'Simulation time: ' + time;
+    const speed = (cpuPerf.update() * 100).toFixed(0);
+    statusLabel.textContent = `Simulation time: ${time} (${speed}%)`;
   });
 }