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9

About 0.6 to 1 ms after the last one is read. The 8042 keyboard controller does not queue scancodes; it just stops receiving bits from the keyboard until a byte is read from port 0x60. When a scancode byte is read out, the controller gets ready to receive another byte from the keyboard. But since serial communication is not instantaneous, actually receiving ...


9

[Caveat, this is from memory, and about a real PC-AT, with real, 16 bit BIOS and code] TL;DR: When does an IBM-compatible PC keyboard controller dequeue scancodes? (I assume this is about a PC-AT, not a PC or PC-XT) Never, as there is no queue. At least none in hardware. The 8042 has simply 4 registers Data In/Out, Status and Command. All synchronisation ...


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