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Date: Fri, 21 Feb 1997 19:33:58 +1000 (EST)
From: Stephen McKay <syssgm@devetir.qld.gov.au>
Message-Id: <199702210933.TAA27694@ogre.devetir.qld.gov.au>
To: dpb@kafka.hqs.crc.com
cc: freebsd-bugs@freebsd.org, syssgm@devetir.qld.gov.au
Subject: Re: kern/2787: Cyrix 150+ CPU is seen as a 486, Kernels made for i586 don't recognize the chip as 586.
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dpb@kafka.hqs.crc.com wrote:

>At boot time, Freebsd sees the Cyrix 150+ (120Mhz) as a 486 instead of a 
>Pentium 120.  When I build a kernel with the i586 option,  it fails 
>to boot, the error "unrecognized cpu" so I must re-make the kernel with 
>the i486 option instead - and loose performance.

A Cyrix 686 has none of the Pentium features that I586_CPU selects.  From
an instruction set perspective it is a 486.  But it plugs into a Pentium
socket.  Run it with I486_CPU defined.  That is your only option.

Basically, the CPU naming game is pretty complex now, and is likely to get
worse when Cyrix releases the M2 and Intel releases Klamath.  It seems to
me that I386_CPU and I486_CPU were good names, but I586_CPU and I686_CPU are
not.  We could replace them all with: CPU_386, CPU_486, CPU_PENTIUM,
CPU_PENTIUM_PRO, CPU_CYRIX_M1, etc.  Or we could conditionalise on the
feature bits (and probably add some more of our own), without relying much
on the actual CPU type.  With MMX (and maybe other stuff) it looks like you
have to anyway.

Stephen.

PS  Umm, how does one close a PR?  Or re-label it as a handbook/doc PR?