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Friday, February 26, 2021

TRACKING WITH CLOSEUPS: Top Ten Craziest x86 Instructions

The Intel x86 “architecture” (if you can call it that) is the most amazing collection of bags hanging on the side of bags bulging with kludges hacked over a long history of providing absurdly complicated instructions almost nobody uses lest their code not run on older processors that don't implement them. Here are some of the most egregious examples.

I have actually used one of these instructions: can you guess which? I remember giggling when I learned the Univac 1107 had an instruction called “Magnitude of Characteristic Difference to Upper”. Imagine the progress that fifty years would bring!

Posted at February 26, 2021 12:19