maximum of CPUs

John Baldwin jhb at
Wed Jul 16 11:59:59 PDT 2003

On 16-Jul-2003 Cagle, John (ISS-Houston) wrote:
>> -----Original Message-----
>> From: John Baldwin [mailto:jhb at] 
>> On 15-Jul-2003 Cagle, John (ISS-Houston) wrote:
> <SNIP>
>> > --
>> > I/O APICs:      APIC ID Version State           Address
>> >                  8       0x11    usable          0xfec00000
>> >                  9       0x11    usable          0xfec01000
>> >                 10       0x11    usable          0xfec02000
>> > 
>> > Is this what you would expect to see on an 8-way server 
>> that supports
>> > hyperthreading?
>> Ugh, I would hope that the APIC ID's wouldn't collide with CPUs. :(
>> Note that you have real CPU's at ID's 8 and 10 and a logical one at
>> 9.  Currently my code doesn't renumber APIC ID's to try to cope with
>> this type of case.  Does the ACPI MADT table report the same values
>> for the APIC ID's of the I/O APICs?
> I should have updated my BIOS before trying this out.  Sure enough, this
> was a BIOS bug that was corrected in March.  The I/O APICS are now
> numbered 16, 17 & 18 so as to not collide with processor's local APICS.
> (Looks like the original BIOS only accounted for processors 0..7,
> without hyperthreading.)

Ok, good.

> However, even with the properly renumbered IOAPICs, I still get the same
> panic: "No free physical APIC IDs found".

This is still expected with the current code.

> I'm going to add some debug messages and track this down further.  I'll
> let you know if I find anything.  I'll also check the MADT to see if it
> jives with everything else.

Tor's suggestion to bump up NAPICID to 256 might help.


John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve!"  -

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