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SubjectRe: [OT] fpu IRQ x86-ism
Riley Williams wrote:
>
> Hi Peter.
>
> >> Sorry for this somewhat OT question - I'll try to be brief.
> >> I have always noticed that on x86 Linux boxes, IRQ 13 is
> >> for the FPU and is always "1" (I assume this is from
> >> probing or testing at bootup). This value never seems to
> >> change, so again I will assume that it is only used to
> >> signal FPU errors. There is no "fpu IRQ" on my Alpha,
> >> obviously it has an FPU as well. Is it's existance on the
> >> PC just some lame legacy issue?
>
> > Yup. It isn't even used to signal FPU errors on 486+ PCs.
>
> Does that mean it's available for use by other hardware, or is
> that prohibited by other considerations?
>

It's not -- there is no wire that can be used to raise IRQ 13 from any
other device.

-hpa

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