On Fri, 26 Aug 2005, Martin Wilck wrote: > Unless I am mistaken, the MP spec does not say that _CPUs_ must start from 0. > We had an IO-APIC at 0. The MP spec says that the IDs must be unique (I am > told this isn't true any more because an IO APIC and a CPU may have the same > ID) and _need not_ be consecutive.
You are unfortunately mistaken -- the spec is explicit about *local* APIC IDs having to start at 0. There are at least two places in the spec that refer to that. > We tried different setups; one had IO APICs at 0,1,2 and CPUs starting at 16. > I can't see that this is forbidden (the reason is that the IO-APICs have only > 4-bit APIC ID registers). Anyway we changed it now to have both IO-APICs and > CPUs start at 0. You can always assign 0, 16, 17, etc. to local APICs and then 1, 2, 3, etc. for I/O APICs. Frankly I don't know what the actual justification behind the requirement is. Note that the ID of 0 need not necessarily belong to the BSP. Maciej - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/