Cyrix III processor and kernel boot problem

Cyrix III processor and kernel boot problem

[c1cc10]

Hello,
I made an unsuccessfull search on the m-l archive about this problem, so 
now I'm going to report it in the developing m-l.
I own a Cyrix III processor (400 Mhz up to 800Mhz) on a via chipset 
motherboard. When I boot with a kernel compiled for Cyrix processor or 
with a 686 pentium the lilo gets the images, put it on memory and 
decompress it, but when it has to boot (after the "Loading 
mlinuz..........") it always reboot the computer.
I've found out that the Cyrix III has no CMOV instruction and that this 
could be the problem.
So I compiled a pentium mmx version (after mrproper and dep) and all 
worked fine.
My question is: ok, it can't work if 686 compiled, but why does not it 
work also for the Cyrix III version?

I tried a "vanilla" kernel and some htb pathced one.
kernel versions: 2.4.19 and 2.4.20.
hope my report will help

keep up the good work

feel free to contact me

bye

c1cc10
-- 
pub  1024D/76A9AC52 2002-12-13 ciunociciunozero (PORCODIO) <c1cc10@ecn.org>
      Key fingerprint = 64A9 9498 B297 B49F D676  AAA1 9DA9 CABA 76A9 AC52
sub  2048g/F248FA79 2002-12-13 [expires: 2004-12-12]

Re: Cyrix III processor and kernel boot problem

[Dave Jones]

On Fri, Feb 07, 2003 at 02:50:02PM +0000, c1cc10 wrote:
 > I've found out that the Cyrix III has no CMOV instruction and that this 
 > could be the problem.
 > So I compiled a pentium mmx version (after mrproper and dep) and all 
 > worked fine.
 > My question is: ok, it can't work if 686 compiled, but why does not it 
 > work also for the Cyrix III version?

The CyrixIII compile option should not generate cmov.
If you can objdump -D vmlinuz and grep for cmov, and find out
where thats being generated to confirm that it is that could be useful.

Which gcc did you use? And (silly question), did you make mrproper
before building the cyrix3 kernel ? If there were left behind .o
files, that could confuse it. Possibly ccache too.
if you were using that rm -rf ~/.ccache to be sure.

as a sidenote, the new C3s (Nehemiah) now have CMOV.

		Dave

-- 
| Dave Jones.        http://www.codemonkey.org.uk
| SuSE Labs

Re: Cyrix III processor and kernel boot problem

[P]

Dave Jones wrote:
> On Fri, Feb 07, 2003 at 02:50:02PM +0000, c1cc10 wrote:
>  > I've found out that the Cyrix III has no CMOV instruction and that this 
>  > could be the problem.
>  > So I compiled a pentium mmx version (after mrproper and dep) and all 
>  > worked fine.
>  > My question is: ok, it can't work if 686 compiled, but why does not it 
>  > work also for the Cyrix III version?
> 
> The CyrixIII compile option should not generate cmov.
> If you can objdump -D vmlinuz and grep for cmov, and find out
                         ^^^^^^^ -> vmlinux-2.4.20

> as a sidenote, the new C3s (Nehemiah) now have CMOV.

but no 3dnow so older C3 specific kernels don't work!

Pádraig.

Re: Cyrix III processor and kernel boot problem

[Dave Jones]

On Fri, Feb 07, 2003 at 02:17:39PM +0000, P@draigBrady.com wrote:

 > >as a sidenote, the new C3s (Nehemiah) now have CMOV.
 > but no 3dnow so older C3 specific kernels don't work!

Yep. Dropped in favour of SSE.  I have a patch to add an extra
config option for the C3-2. It's going to Linus/Marcelo later
this afternoon.

		Dave

-- 
| Dave Jones.        http://www.codemonkey.org.uk
| SuSE Labs

Re: Cyrix III processor and kernel boot problem

[c1cc10]

Dave Jones wrote:

> Which gcc did you use? And (silly question), did you make mrproper
> before building the cyrix3 kernel ? If there were left behind .o
> files, that could confuse it. Possibly ccache too.
> if you were using that rm -rf ~/.ccache to be sure.

ok, I'll jump directly to the point: I did not make any mrproper.
after your answer I tried and it worked.
sorry for the false alarm

c1cc10
-- 
pub  1024D/76A9AC52 2002-12-13 ciunociciunozero (PORCODIO) <c1cc10@ecn.org>
      Key fingerprint = 64A9 9498 B297 B49F D676  AAA1 9DA9 CABA 76A9 AC52
sub  2048g/F248FA79 2002-12-13 [expires: 2004-12-12]

Re: Cyrix III processor and kernel boot problem

[Alan Cox]

On Fri, 2003-02-07 at 14:50, c1cc10 wrote:
> I've found out that the Cyrix III has no CMOV instruction and that this 
> could be the problem.

It is

gcc told to build for i686 assumes that cmov is present. Much of the 
code advantage for i686 comes from cmov so it makes sense to do that
I guess.

The optimal kernel for the CyrixIII/VIA-C3 is the the Cyrix III/VIA-C3
option in current kernel menus, or i486

Alan

Re: Cyrix III processor and kernel boot problem

[H. Peter Anvin]

Followup to:  <1044631346.14350.17.camel@irongate.swansea.linux.org.uk>
By author:    Alan Cox <alan@lxorguk.ukuu.org.uk>
In newsgroup: linux.dev.kernel
>
> On Fri, 2003-02-07 at 14:50, c1cc10 wrote:
> > I've found out that the Cyrix III has no CMOV instruction and that this 
> > could be the problem.
> 
> It is
> 
> gcc told to build for i686 assumes that cmov is present. Much of the 
> code advantage for i686 comes from cmov so it makes sense to do that
> I guess.
> 

Yep.  The other name for the option, -mach=pentiumpro, really is the
more proper name.

	-hpa
-- 
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