Re: 2us Interrupt latency's for Linux 2.0.xx

Gregory Maxwell (linker@z.ml.org)
Fri, 4 Sep 1998 01:24:23 -0400 (EDT)


On Thu, 3 Sep 1998, George wrote:

> On Wed, 2 Sep 1998, Perry Harrington wrote:
>
> >I'm wondering, can the APIC be enabled for UP boards? If so, why
> >doesn't Linux enable the APIC as the default interrupt controller
> >for single processor Pentium+ systems?
>
> Single processor boards don't have an APIC or IO-APIC. If you read
> Documentation/SMP.txt, the note:
>
> o Separate IO-APIC from SMP.
>
> means it's on the agenda to allow the IO-APIC to be used by uniprocessor
> kernels running on SMP boards. (which, incidently, NT 4.0 can do.)
>
> -George

If NT uses the IO-APIC then why is it limited to the 16 normal INTs?
Furthermore, if they use IO-APIC how could they screw up their int
handling so badily their their int latency is so high dispite the ultra
fast IO-APIC.

Perhaps NT 4.0 uses IO-APIC in that it detects it's presence.

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