CPU detection for Cyrix 6x86

CPU detection for Cyrix 6x86

Post by Wynstan To » Tue, 23 Jul 1996 04:00:00



Hi,

        I am one of those who has chosen 6x86 for the CPU upgrade.  However,
it seems that the CPU detection code in Linux's kernel is UNABLE to report
correctly what type of CPU I am using.  I urge for somebody who knew and was
interested to write a patch for that.  But anyway, is there any work on-going?

--
Wynstan

 
 
 

CPU detection for Cyrix 6x86

Post by H.J. Gibs » Thu, 25 Jul 1996 04:00:00


: Hi,

:       I am one of those who has chosen 6x86 for the CPU upgrade.  However,
: it seems that the CPU detection code in Linux's kernel is UNABLE to report
: correctly what type of CPU I am using.

Ditto.  Fortunately, it seems to go extremely fast, even with Linux
thinking it is a 486 etc..   AND giving it a rather poor Bogomips score.
        My own tests seem to indicate it is flying along.
How much better if Linux recognised it!?
        H. Gibson

 
 
 

CPU detection for Cyrix 6x86

Post by Roderick W. Smi » Fri, 26 Jul 1996 04:00:00



Gibson)24 Jul 1996 21:34:54 GMT writes:


> :
> : I am one of those who has chosen 6x86 for the CPU upgrade.
> : However, it seems that the CPU detection code in Linux's kernel is
> : UNABLE to report correctly what type of CPU I am using.

> Ditto.  Fortunately, it seems to go extremely fast, even with Linux
> thinking it is a 486 etc..   AND giving it a rather poor Bogomips
> score.
>    My own tests seem to indicate it is flying along.
> How much better if Linux recognised it!?

My understanding is that the 6x86 runs better with code that's optimized for the
486 than with code that's optimized for the Pentium.  I confess that I don't
know what, if anything, Linux's kernel does with the information of what CPU's
being run; but I'd suggest NOT optimizing code to be run on a 6x86 for a
Pentium; set the compiler to 486 mode.  If somebody's got better advice, please
post it.

+----------------------------------------------------------------+
| Rod Smith                             Author of:               |

| http://psych.colorado.edu/~rsmith     "OS/2 Soundcard Summary" |
+----------------------------------------------------------------+

 
 
 

CPU detection for Cyrix 6x86

Post by Oleg Duli » Sat, 27 Jul 1996 04:00:00


I am also upgrading my computer to 6x86. I've read that Linux works on
6x86 perfectly, doesn't it? So, why bother detecting the CPU?

--------------------------------------------------------------------------
Oleg Dulin, Clarkson University student number 40937
URL: http://www.clarkson.edu/~dulino


Quote:> Hi,

>    I am one of those who has chosen 6x86 for the CPU upgrade.  However,
> it seems that the CPU detection code in Linux's kernel is UNABLE to report
> correctly what type of CPU I am using.  I urge for somebody who knew and was
> interested to write a patch for that.  But anyway, is there any work on-going?

> --
> Wynstan

 
 
 

CPU detection for Cyrix 6x86

Post by Wynstan To » Sun, 28 Jul 1996 04:00:00


Hi Roderick,

        Oh, yes.  Only the M2 will support MMX.  Sorry for the confusion.  I also
agree that the 6x86 is running a bit faster on 486-code.  But whenever I look
at my /proc/cpuinfo,

processor       : 0
cpu             : 486
model           : unknown
vendor_id       : unknown
stepping        : unknown
fdiv_bug        : no
hlt_bug         : no
fpu             : yes
fpu_exception   : yes
cpuid           : no
wp              : yes
flags           :
bogomips        : 119.60

        I will be so upset that some of the items are just "unknown".  Would it be
nice to give them some names instead of just filling blanks?  In fact, writing
codes to extract the CPUID for 6x86 is not that hard since the IBM 6x86 has
already released the BIOS writer guide on their web.  The assembly code is
just right inside.  If somebody is interested and have time, please give it
a try.  Thanks a lot.  :-)

Just my thought,
Wynstan

 
 
 

CPU detection for Cyrix 6x86

Post by Roderick W. Smi » Sun, 28 Jul 1996 04:00:00





> : I am also upgrading my computer to 6x86. I've read that Linux
> : works on 6x86 perfectly, doesn't it? So, why bother detecting the
> : CPU?

> It does have some points to have the kernel recognize it.  As it
> claims, Cyrix 6x86 should support MMX codes.

'Fraid not.  Cyrix's M2 chip (in development) is supposed to support MMX
extensions, but the currently shipping 6x86 does not.

Quote:> If, possibly in the future, some programs need to detect for the
> CPUID in order to turn the functions on, will it be a bug to regard
> it as 4x86?  6x86 is actually different from a Intel's Pent...

I honestly don't know if the Linux kernel could currently use any 6x86-specific
features if it knew it was running on a 6x86.  I do know that the 6x86 handles
code optimized for the 486 better than it handles code optimized for the Pentium
(I tried compiling kernel 2.0.7 with each optimization, and the BogoMips value
was halved when going from 486 to Pentium optimizations, if that means
anything).

+----------------------------------------------------------------+
| Rod Smith                             Author of:               |

| http://psych.colorado.edu/~rsmith     "OS/2 Soundcard Summary" |
+----------------------------------------------------------------+

 
 
 

CPU detection for Cyrix 6x86

Post by Wynstan To » Sun, 28 Jul 1996 04:00:00


: I am also upgrading my computer to 6x86. I've read that Linux works on
: 6x86 perfectly, doesn't it? So, why bother detecting the CPU?

    It does have some points to have the kernel recognize it.  As it claims,
Cyrix 6x86 should support MMX codes.  If, possibly in the future, some programs
need to detect for the CPUID in order to turn the functions on, will it be a
bug to regard it as 4x86?  6x86 is actually different from a Intel's Pent...

Just my opinion,
--
Wynstan

 
 
 

CPU detection for Cyrix 6x86

Post by Stephen Knila » Mon, 29 Jul 1996 04:00:00




>: Hi,

>:   I am one of those who has chosen 6x86 for the CPU upgrade.  However,
>: it seems that the CPU detection code in Linux's kernel is UNABLE to report
>: correctly what type of CPU I am using.

>Ditto.  Fortunately, it seems to go extremely fast, even with Linux
>thinking it is a 486 etc..   AND giving it a rather poor Bogomips score.
>    My own tests seem to indicate it is flying along.
>How much better if Linux recognised it!?
>    H. Gibson

Several people have said that it does BETTER with 486 opt, rather than pent!
Hence, if it recognized it as a pent, it would go SLOWER!  BTW the speed
difference in this case is due to the compiler, and options given to kernel
compile.  The proc is for info only(with regard to CPU type).

Steve

 
 
 

CPU detection for Cyrix 6x86

Post by Roderick W. Smi » Mon, 29 Jul 1996 04:00:00



Quote:Knilans) writes:

> Several people have said that it does BETTER with 486 opt, rather
> than pent! Hence, if it recognized it as a pent, it would go SLOWER!

Only if the kernel (or whatever other program is attempting to ID the CPU) has
both 486 and Pentium optimizations compiled into one executable, and code to
execute whichever is more appropriate; and also only if the CPU ID code thought
the 6x86 was a Pentium, as opposed to a 6x86 (if it IDed it as a 6x86, it'd
presumably execute the 486 code instead of the Pentium code, at least if it were
intelligently programmed).

Quote:> BTW the speed difference in this case is due to the compiler, and
> options given to kernel compile.

Precisely; this is a COMPILE-TIME option which has a RUN-TIME effect.

+----------------------------------------------------------------+
| Rod Smith                             Author of:               |

| http://psych.colorado.edu/~rsmith     "OS/2 Soundcard Summary" |
+----------------------------------------------------------------+

 
 
 

CPU detection for Cyrix 6x86

Post by Brynn Roger » Tue, 30 Jul 1996 04:00:00






> > : I am also upgrading my computer to 6x86. I've read that Linux
> > : works on 6x86 perfectly, doesn't it? So, why bother detecting the
> > : CPU?

> > It does have some points to have the kernel recognize it.  As it
> > claims, Cyrix 6x86 should support MMX codes.

> 'Fraid not.  Cyrix's M2 chip (in development) is supposed to support MMX
> extensions, but the currently shipping 6x86 does not.

> > If, possibly in the future, some programs need to detect for the
> > CPUID in order to turn the functions on, will it be a bug to regard
> > it as 4x86?  6x86 is actually different from a Intel's Pent...

> I honestly don't know if the Linux kernel could currently use any 6x86-specific
> features if it knew it was running on a 6x86.  I do know that the 6x86 handles
> code optimized for the 486 better than it handles code optimized for the Pentium
> (I tried compiling kernel 2.0.7 with each optimization, and the BogoMips value
> was halved when going from 486 to Pentium optimizations, if that means
> anything).

The 6x86 has pentium sized pages (4MB) or 486 size pages (4K ?), it also
has
Cyrix sized pages (apparently varible sized between 4K and 4M ?).

I would think the that the kernel would be at an advantage if it used
the
pentium sized pages ( and maybe still the 486 optimizations?).

The 6x86 can also finish instructions out-of-order.  So can the pentium
Pro.
there are region registers that you can disable this for specific
regions on
both the PentiumPro and the 6x86 [like a Memory-mapped IO card].   I
would
presume that using this feature would also be advantageous (sp?) to the
kernel.

My motherboard BIOS correctly recognizes the CPU as a Cyrix-6x86 P166+
,  and I also
think it probably disables some of these features.  Sooo,  I am looking
at
making the linux kernel recognize the 6x86 and use the best mix of
features of it.

Brynn

 
 
 

1. File Descriptors per Process and Cyrix 6x86 CPU Questions...

Hi...  I was just wondering how you can recompile the FreeBSD 2.1.7-2.2.0 to
allow 1024 File Descriptors (FDs) per process.  The default it 256
FDs/process.  Also... will there be support for Cyrix 6x86 processors in
future versions of FreeBSD or does it not matter? :)... right now it thinks my
CPU is a Cyrix 486DX (I have one of those in the other room) :)

--
Eric Futch

http://www.nyct.net
http://www.nyct.net/~efutch
New York Connect --- Powered by FreeBSD

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