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Questions tagged [cpu-flag-bits]

Condition flags describing the state of the CPU or the result of an operation it performed.

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23 votes
1 answer
898 views

How is FSTSW AX implemented on the 80286/80287?

The x87 instruction set does not support direct transfers between general purpose registers and floating point registers. This is mainly a consequence of the 8087/80287/80387 being a separate chip ...
fuz's user avatar
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20 votes
5 answers
4k views

Why does the Z80 have a half-carry bit?

The Z80 apparently had a 4-bit ALU, and computes 8-bit values in two stages. The half-carry bit preserves the carry from bits 3 to 4. Why did the designers of this chip choose to preserve that value ...
Omar and Lorraine's user avatar