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Date: Sat, 08 Nov 1997 11:51:03 +0800
From: Doug Lo <jwlo@ms11.hinet.net>
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To: Julian Elischer <julian@whistle.com>
CC: freebsd-hackers@FreeBSD.ORG
Subject: Re: Newest Pentium bug (fatal)
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You wrote:

> On a "genuine Intel" pentium (not pentium pro)
> execution of the following sequence, 0xf0 0x0f 0xc7 0xc8
>
> will stop the processor. This is doable from user mode and in
> 16bitmode, or in fact any mode.
>
> try the following c program.
>
> unsigned char x[] = { 0xf0, 0x0f, 0xc7, 0xc8 };
>
> main ()
> {
>   void (*f)(void) = x;
>   f();
> }
>
> We've checked:
> K5... OK
> P6...  OK
> P5...   *SPLAT*
>
> no idea about the pentium II or other pentium copies.
> K6?
>
> other pentium variants?
> versions?
>
> this one DEFINITLY dies:
> CPU: Pentium (99.38-MHz 586-class CPU)
>   Origin = "GenuineIntel"  Id = 0x525  Stepping=5
>   Features=0x1bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8>
>

Julian,

I tried it. Also crashes.

CPU: Pentium (132.96-MHz 586-class CPU)
Origin = "GenuineIntel"  Id = 0x526  Stepping=6
Features=0x1bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8>

BTW, would anyone tell me what these arguments mean(0xf0, 0x0f, 0xc7,
0xc8)?

Regards,
Doug.