Re: [2.1.105] Cyrix 6x86 reduced to 486

Stephen Kitt (steve@tardis.ed.ac.uk)
Fri, 12 Jun 1998 13:34:10 +0100

On Tue, Jun 09, 1998 at 11:10:56PM -0400, Phil's Kernel Account wrote:
> it's going to come back as soon as I can find enough time between dealing
> with contract jobs, email, and the phone, to do some SERIOUS CPU detection
> work. Fun, yeah. }:P

You might have thought of this already (in fact, ISTR Alan Cox posted
something like this when the problem was first detected), but the following
should work:

* check 386, 486 as usual
* check CPUID, if not present, <= 486, NexGen, or 6x86 (non-L) with CPUID
disabled (or rather, not yet enabled :-)
* use CPUID to determine which type of CPU is really present
* if and only if Intel Pentium II or later, check for BX

The precise checks for Cyrix CPU types using the problem ports only occurs
when we're sure we can't have BX - ie, we've not got CPUID or CPUID tells us
we've got a Cyrix chip. Of course, this relies on Intel not starting to
identify PIIs as CyrixInstead...

I also STR reading somewhere than IDT WinChips can have various manufacturer
ID's... But that shouldn't affect the Cyrix/Pentium II w/ BX detection.

Stephen

-- 
  Stephen Kitt - steve@tardis.ed.ac.uk - http://www.tardis.ed.ac.uk/~steve
 PGP key ID 1024/732B6FA5 - finger -l kitt@finger.tardis.ed.ac.uk for block
	   "It's kind of fun to do the impossible" -- Walt Disney


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