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 :) Thanks, tglx