Fun fact: Just like microcontrollers, the fuse bits in desktop CPUs can occasionally get loose, causing single-bit flips. This is likely responsible for many strange CPUIDs in the wild, some reported cases include "GenuineIotel" CPUs [1] and a "Intel Core i4" CPU. [2] #electronics
@niconiconi the real question is when will the bit turning off the rest of the cores in the ccx in my cpu flip on its own and my ryzen 5 5600 will magically become a ryzen 7 5700x (slightly overclocked and with the wrong cpuid and probably busted cores)
@LockEx Not just "attributed", it's an experimental fact. But it's likely irrelevant in the case I've showed here. In this case it's not volatile DRAM data corruption that would disappear after a reboot, it's a case of permanent data corruption within the non-volatile ROM. DRAM is volatile and easy to flip by cosmic rays, ROM is not easy. It's still possible to flip a Flash or ROM cell via radiation, but only when it's flying in the outer space. Most likely it's just a natural failure mode of ROM/Flash due to charge leakage.
@LockEx If you're interested, here are some great technical standards that explain the problem of data corruptions from cosmic rays by the International Telecommunication Union. I've shared previously, reposting for visibility...
K.130 : Neutron irradiation test methods for telecommunication equipment (yes, apparently some people already started testing telecom equipment in critical infrastructure using a particle accelerator) https://www.itu.int/rec/T-REC-K.130-202201-I/en
@niconiconi I am currently in the midst of writing a paper on CPUID trickery that has taken me years to complete and only now do I find out that it's not immutable??
@gsuberland The fuse bits (at least those that control the marketing name) are likely controlled by a EEPROM with write protection, just like microcontrollers. Gamers Nexus's AMD tour video had a section about how CPU SKUs are programmed by fuse bits from JTAG. Another fun fact: on AMD, the "model name" part of the CPUID is (temporarily) overwrittable by OS via MSR. https://chipsandcheese.com/2022/10/27/why-you-cant-trust-cpuid/
@jpm@niconiconi true, but even if you set the bar at "you can modify this without using a delidding tool and a very fancy optical train and a pulsed UV laser" most SoVs are still divorced from reality.
@niconiconi@gsuberland I thought the model name was set by the bios (or maybe microcode?) on some devices. Also note in a VM the hypervisor can make anything up there.
@niconiconi@gsuberland Then with some electron beam trickery I'm pretty sure some scientists will rewrite those EEPROM for fun and get really funny CPU names.
PS: Saying this because I know someone in second year of their master in computer science that had to read and report on scientists hacking into AIs running on GPUs. By using an electron beam to break the AI.
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