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Comment by hnthrowaway0315

11 hours ago

Hi kens, thanks for the knowledge sharing all these years. Can you please confirm this one? From Wikipedia, it says that 8087 uses CORDIC algorithm. Does that mean that it's the same (but different speed) as what I'd implement the functions in software, except in microcode (which has more granularity than usual assembly code)?

I found it a bit surprising that as a 45-year old chip, there is no public information of its microcode. I guess hardware is indeed much more secret than software.

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hnthrowaway0315

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kens  11 hours ago

Yes, the 8087 uses CORDIC. I extracted the constants from the 8087's internal constant ROM and they are arctangent and log values for the CORDIC algorithm. You can implement the same functions in software, which is what floating-point emulation libraries did back then.

There's almost no public information on the 8087 microcode, but I'm working on that :-)