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fix: repeated keyboard input when INT 16h polls an empty 8042 buffer #2320

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fix: repeated keyboard input when INT 16h polls an empty 8042 buffer #2320

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9 changes: 9 additions & 0 deletions src/Spice86.Core/Emulator/InterruptHandlers/Input/Keyboard/BiosKeyboardInt9Handler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,15 @@ public BiosKeyboardInt9Handler(IMemory memory, BiosDataArea biosDataArea,

/// <inheritdoc />
public override void Run() {
// INT 16h may invoke INT 09h as a polling mechanism.
// Do not reprocess the controller's previous data byte when
// the output buffer contains no new data.
byte status = _ps2Controller.ReadByte(KeyboardPorts.StatusRegister);
if ((status & 0x01) == 0) {
_dualPic.AcknowledgeInterrupt(1);
return;
}

// Disable keyboard first - otherwise Prince of Persia reads it before us!
_ps2Controller.WriteByte(KeyboardPorts.Command, (byte)KeyboardCommand.DisablePortKbd);

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