diff --git a/run/index.html b/run/index.html
index 22ee96b1..cf9c4d96 100644
--- a/run/index.html
+++ b/run/index.html
@@ -9,6 +9,7 @@
 <script type="module" src="../squeak.js"></script>
 <script>
     function runSqueak(imageName) {
+        // Squeak.debugFiles = true;
         sqText.style.display = "none";
         sqCanvas.style.display = "block";
         SqueakJS.runSqueak(imageName, sqCanvas,{
@@ -230,9 +231,9 @@ <h2>Run Squeak images from the internet</h2>
         <li>Squeak 5.0 (2015) <a href="#url=https://freudenbergs.de/vanessa/squeakjs&zip=[Squeak5.0-15113.zip,SqueakV50.sources.zip]">link</a></li>
         <li>SpeechPlugin Demo (2016) <a href="#zip=https://www.hpi.uni-potsdam.de/hirschfeld/artefacts/squeakjs/SpeechPluginDemo.zip">link</a></li>
         <li>Squeak 6.0 64 bit (2022) <a href="#zip=https://files.squeak.org/6.0/Squeak6.0-22104-64bit/Squeak6.0-22104-64bit.zip">link</a></li>
-        <li>Cuis 6.2 (2023) <a href="#highdpi=true&url=https://cdn.jsdelivr.net/gh/Cuis-Smalltalk/Cuis6-2@6f984e8c/CuisImage&files=[32BitImages/Cuis6.2-32.image,32BitImages/Cuis6.2-32.changes,Cuis6.2.sources]">link</a></li>
+        <li>Cuis 6.2 (2023) <a href="#highdpi&url=https://cdn.jsdelivr.net/gh/Cuis-Smalltalk/Cuis6-2@6f984e8c/CuisImage&files=[32BitImages/Cuis6.2-32.image,32BitImages/Cuis6.2-32.changes,Cuis6.2.sources]">link</a></li>
         <li>Squeak Trunk 6.1α (2024) <a href="#zip=https://files.squeak.org/6.1alpha/Squeak6.1alpha-22998-32bit/Squeak6.1alpha-22998-32bit.zip">link</a></li>
-        <li>Squeak Trunk 6.1α (hi-res: save image after first load for faster startup) <a href="#highdpi=true&zip=https://files.squeak.org/6.1alpha/Squeak6.1alpha-22998-32bit/Squeak6.1alpha-22998-32bit.zip">link</a></li>
+        <li>Squeak Trunk 6.1α (hi-res: save image after first load for faster startup) <a href="#highdpi&zip=https://files.squeak.org/6.1alpha/Squeak6.1alpha-22998-32bit/Squeak6.1alpha-22998-32bit.zip">link</a></li>
         </ul>
         On the first run these will be stored locally. Subsequent starts are much faster since there is no download.
 
diff --git a/squeak.js b/squeak.js
index 718bf02e..6b275e18 100644
--- a/squeak.js
+++ b/squeak.js
@@ -38738,6 +38738,7 @@
             vmProxy: null,
             vm: null,
             prims: null,
+            timeOffset: 0,
             midi: null, // WebMIDI access or false if not supported
             midiPromise: null,
             ports: new Map(), // indexed by Squeak port number
@@ -38770,6 +38771,7 @@
                         this.midi = false;
                     });
                 }
+                if (performance.timeOrigin) this.timeOffset = performance.timeOrigin - this.vm.startupTime;
             },
             initMIDI(access) {
                 const allPorts = [...access.inputs.values(), ...access.outputs.values()];
@@ -38794,9 +38796,6 @@
                     console.log(`MIDIPlugin: port ${portNumber} ${dir} (${names.join(', ')})`);
                 }
             },
-            clock() {
-                return performance.now() & Squeak.MaxSmallInt;
-            },
             portChanged(port) {
                 // Squeak likes combined input/output ports so we create sqPorts with input+output here
                 let { name, manufacturer } = port;
@@ -38820,22 +38819,24 @@
                         input: null,
                         output: null,
                         runningStatus: 0,
-                        receivedData: [],
+                        receivedMessages: [],
                     };
                     this.ports.set(handle, sqPort);
                 }
-                // update port
-                sqPort[port.type] = port;
-                sqPort.dir |=  port.type === 'input' ? 1 : 2; // 1=input, 2=output, 3=input+output
+                // dir: 1=input, 2=output, 3=input+output
+                if (port.state === "connected") {
+                    sqPort[port.type] = port;
+                    sqPort.dir |=  port.type === 'input' ? 1 : 2;
+                } else {
+                    sqPort[port.type] = null;
+                    sqPort.dir &= port.type === 'input' ? ~1 : ~2;
+                }
                 return sqPort;
             },
             primitiveMIDIGetPortCount(argCount) {
                 // we rely on this primitive to be called first
                 // so the other primitives can be synchronous
-                const returnCount = () => {
-                    const count = this.midi ? this.midi.outputs.size : 0;
-                    return this.vm.popNandPush(argCount + 1, count);
-                };
+                const returnCount = () => this.vm.popNandPush(argCount + 1, this.ports.size);
                 if (this.midi === null) {
                     const unfreeze = this.vm.freeze();
                     this.midiPromise
@@ -38855,7 +38856,9 @@
                 const portNumber = this.prims.stackInteger(0);
                 const port = this.ports.get(portNumber);
                 if (!port) return false;
-                return this.prims.popNandPushIfOK(argCount + 1, this.prims.makeStString(port.name));
+                let name = port.name;
+                if (port.dir === 0) name += ' [disconnected]';
+                return this.prims.popNandPushIfOK(argCount + 1, this.prims.makeStString(name));
             },
             primitiveMIDIGetPortDirectionality(argCount) {
                 if (!this.midi) return false;
@@ -38866,7 +38869,8 @@
             },
             primitiveMIDIGetClock(argCount) {
                 if (!this.midi) return false;
-                return this.prims.popNandPushIfOK(argCount + 1, this.clock());
+                const clock = this.prims.millisecondClockValue();
+                return this.prims.popNandPushIfOK(argCount + 1, clock);
             },
             primitiveMIDIParameterGetOrSet(argCount) {
                 if (!this.midi) return false;
@@ -38902,7 +38906,11 @@
                 let port;
                 const checkPort = () => {
                     port = this.ports.get(portNumber);
-                    if (!port) console.error('MIDIPlugin: invalid port ' + portNumber);
+                    if (!port) console.error(`MIDIPlugin: invalid port ${portNumber}`);
+                    else if (!port.dir) {
+                        console.error(`MIDIPlugin: port ${portNumber} ${port.name} is disconnected`);
+                        port = null;
+                    }
                 };
                 const openPort = unfreeze => {
                     const promises = []; // wait for MIDI initialization first
@@ -38913,12 +38921,14 @@
                         if (port.output.connection === "closed") promises.push(port.output.open());
                         else console.warn(`MIDIPlugin: output port ${portNumber} is ${port.output.connection}`);
                     port.runningStatus = 0;
-                    port.receivedData = [];
+                    port.receivedMessages = [];
                     Promise.all(promises)
                         .then(() => {
                             if (port.input) port.input.onmidimessage = event => {
-                                port.receivedData.push(event.data);
-                                if (this.debug) console.log('MIDIPlugin: received', event.data);
+                                const time = Math.round(event.timeStamp + this.timeOffset);
+                                const bytes = new Uint8Array(event.data);
+                                port.receivedMessages.push({time, bytes});
+                                if (this.debug) console.log('MIDIPlugin: received', time, [...bytes]);
                             };
                         })
                         .catch(err => console.error('MIDIPlugin: ' + err))
@@ -38949,7 +38959,7 @@
                     if (port.input && port.input.connection === 'open') {
                         promises.push(port.input.close());
                         port.input.onmidimessage = null;
-                        port.receivedData.length = 0;
+                        port.receivedMessages.length = 0;
                     }
                     if (port.output && port.output.connection === 'open') {
                         promises.push(port.output.close());
@@ -38988,16 +38998,14 @@
                     data = newData;
                 }
                 try {
-                    if (this.debug) console.log('MIDIPlugin: send', data, timestamp);
+                    if (this.debug) console.log('MIDIPlugin: send', [...data], timestamp);
                     // send or schedule data
                     if (timestamp === 0) port.output.send(data);
                     else port.output.send(data, timestamp);
                     // find last status byte in data, but ignore real-time messages (0xF8-0xFF)
                     // system common messages (0xF0-0xF7) reset the running status
-                    for (let i = data.length-3; i >= 0; i-=2) {
-                        if (data[i] < 0x80) continue; // skip data bytes
-                        if (data[i] >= 0xF8) i -= 1; // skip real-time message
-                        else {
+                    for (let i = data.length - 1; i >= 0; i--) {
+                        if (data[i] >= 0x80 && data[i] <= 0xF7) {
                             port.runningStatus = data[i] < 0xF0 ? data[i] : 0;
                             break;
                         }
@@ -39015,21 +39023,17 @@
                 const port = this.ports.get(portNumber);
                 if (!port || !port.input || port.input.connection !== 'open') return false;
                 let received = 0;
-                let chunk = port.receivedData.shift();
-                while (chunk && received < data.length) {
-                    const free = data.length - received;
-                    if (chunk.length <= free) {
-                        data.set(chunk, received);
-                        received += chunk.length;
-                        chunk = port.receivedData.shift();
-                    } else {
-                        data.set(chunk.subarray(0, free), received);
-                        received += free;
-                        port.receivedData.unshift(chunk.subarray(free));
-                        chunk = null;
-                    }
+                const event = port.receivedMessages.shift();
+                if (event) {
+                    let { time, bytes } = event;
+                    data[0] = (time >> 24) & 0xFF;
+                    data[1] = (time >> 16) & 0xFF;
+                    data[2] = (time >> 8) & 0xFF;
+                    data[3] = time & 0xFF;
+                    data.set(bytes, 4);
+                    received = bytes.length + 4;
+                    if (this.debug) console.log('MIDIPlugin: read', received, [...data.subarray(0, received)]);
                 }
-                if (this.debug) console.log('MIDIPlugin: read', received, data.subarray(0, received));
                 return this.prims.popNandPushIfOK(argCount + 1, received);
             },
         };