Retrocomputing Stack Exchange
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Questions tagged [80286]

The Intel 80286 16-bit microprocessor. Use only for questions specifically about the processor; DO NO USE to mean ‘286-class machine’.

Also known as the iAPX 286 or Intel 286, the 80286 was the first 8086 based CPU with separate, non-multiplexed, address and data buses and also the first with memory management and wide protection abilities.

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How to switch an 80286 from protected to real mode?

It's pretty well documented how to get the 286 from real mode to its 16-bit protected mode. It's also widely stated that the 286 had no officially supported way of going back from protected mode into real mode without losing its current state. The…
user
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How does the 80287 process infinity values?

Modern x86 processors have an infinity control bit on the x87 FPU control register. This is bit 12 and it enables processing of infinity values in a manner that is compatible with the 80287 coprocessor. How does the 80827 process infinity values and…
Single Malt
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Harris 80C286 double fault does not push an error code

I'm using a Harris CS80C286-20 CPU. If I set the access rights byte of the Divide Error Exception descriptor to 0x80 (which indicates a present system descriptor of an invalid type), and then execute the instruction: XOR BX,BX …
lgj1107
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