linux-kernel - Re: What is the best way to identify a new x86 processor that does not implement the CPUID instruction?

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Message-ID: <4899951A.1040704@tmr.com>
Date:	Wed, 06 Aug 2008 08:12:10 -0400
From:	Bill Davidsen <davidsen@....com>
To:	David Wilson <mcs6502@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: What is the best way to identify a new x86 processor that does
 not implement the CPUID instruction?

David Wilson wrote:
> I recently bought a Norhtec MicroClient JrSX which uses the Vortex86sx
> System on Chip processor (see http://vortex86sx.com/ for more
> details). This is identified as a Cyrix 486SLC by the Linux kernel due
> to the lack of a CPUID instruction. While this may be seen as a
> cosmetic defect, if the kernel can identify the processor correctly it
> could, for example, use the clock divisor code provided by the
> manufacturer to slow down and speed up the CPU when required.
> 
> The question is: how to differentiate this chip from the Cyrix part?
> The freely available "brief data sheet" does not provide much detail.
> 
> I have thought of a couple of schemes but am not really keen on either:
> 
> 1) Clock speed - the SoC runs at 300+ MHz while the Cyrix part is < 100 MHz
> 2) Look at the PCI VID/PID for the north bridge as this is part of the CPU die.
> 
> Does anyone have any suggestions? Thanks.

Your (2) sounds reasonable.

-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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