[gamozolabs]

There’s one big public work by utexas that covers this in a few places! https://sites.utexas.edu/jdm4372/2021/05/27/locations-of-cor...

See additional references for PDFs.

I’ve also played around with this in my research kernel, but never thoroughly enough to write up. Something I should revisit, I think it’d be a really fun thing to discuss and work on. Doing this level of timing requires doing BIOS configuration to make the CPU as deterministic as possible (turn off dynamic throttling, make sure you’re thermally keeping the CPU stable, etc).

I always highly encourage people to write advanced benchmarks. It’s a great way to learn how computers work!

[dwattttt]

Sticking with x86, I'm pretty sure CPUID can tell you what the topology of all the cores you can query on are in. Not that I'd tell anyone not to infer it from timing, that just sounds like fun.

[gamozolabs]

It can tell you specified topology, like cores, threads, NUMA nodes. But it can’t tell you the physical locations of cores. Processors are binned based on what cores are functional after fabrication, thus your 12 core processor is probably a 16-18 core processor, and the 4 disabled cores are “random” based on manufacturing defects. Knowing this is completely unimportant, but cool. Ultimately yes, cpuid will tell you and relevant topology, since anything beyond this requires likely trillions of iterations to even detect.