Reverse-engineering the Intel 8087's tangent algorithm: more than CORDIC

Reverse-engineering the Intel 8087's tangent algorithm: more than CORDIC righto.com

I hope you're not tired of the 8087, because I have another article about Intel's floating-point chip. 1 In 1980, Intel introduced the 8087...

125 points•pwg•4 days ago•11 comments•

#intel #algorithm #reverse #engineering #cordic #8087s #tangent #reverse engineering

11 comments

jaygreco4 days ago

Love these deep dives. It’s fascinating to see how real, low-level engineering we all take for granted today unfolded. It’s incredible that the rough equivalent of an entire 160lb digital computer was built and baked into silicon.

Also incredible reverse engineering. In a time when seemingly all appreciation for expertise is gone it’s so refreshing to see.

kens4 days ago

Author here for your 8087 questions...

WalterBright4 days ago

Thank you! Amazing work! I've always had a soft spot for the 8087.

Maybe implement the algorithm in C? Thank would be fun!

jacquesm4 days ago

Weitek next?

kens4 days ago

The 8087 is probably enough floating point for a while :-)

cmovq4 days ago

Always thought it was strange that fptan also pushes 1 to the register stack. It now makes sense it’s so existing code for the 8087 which was expected to do y/x to get the actual tangent could keep working by doing y/1 on newer processors.

heronbank4 days ago

Always fascinated by the low-level cleverness in early hardware. It's a different world from today's abundant resources.

Const-me4 days ago

I remember I once wanted to compute tangent of fp64 vectors. Here’s what I did.

https://github.com/Const-me/AvxMath/blob/master/AvxMath/AvxM...

Read the full thread on Hacker News →

11 comments

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