On 19/04/2023 2:43 pm, Thomas Gleixner wrote: > On Wed, Apr 19 2023 at 14:38, Thomas Gleixner wrote: >> On Wed, Apr 19 2023 at 11:38, Thomas Gleixner wrote: >> IOW, the BIOS assignes random numbers to the AP APICs for whatever >> raisins, which leaves the parallel startup low level code up a creek >> without a paddle, except for actually reading the APICID back from the >> APIC. *SHUDDER* > So Andrew just pointed out on IRC that this might be related to the > ancient issue of the 3-wire APIC bus where IO/APIC and APIC shared the > ID space, but that system is definitely post 3-wire APIC :) Doesn't mean the BIOS code was updated adequately following that. What I'm confused by is why this system boots in the first place. I can only think that's is a system which only has 4-bit APIC IDs, and happens to function when bit 4 gets truncated off the top of the SIPI destination... ~Andrew
