The problem is that the Cyrix MediaGX has a fault in the TSC hardware.
The TSC on the MediaGX does not work correctly all of the time. This is
the reason the TSC is disabled in the Linux code. When X86_FEATURE_TSC
is disabled Linux will compile for i486. I suspect what you are
observing is the faulty TSC. If you really need the TSC then you have a
problem. The MediaGX pins are not compatible with Intel or AMD CPUs.
This means if you want to change to a AMD or Intel CPU to get a working
TSC, you will also have to change to a SBC board that works with AMD and
Intel CPUs.
- Kal.
Yutarou Ebihara wrote:
>
> Hello,
>
> i am from japan, and i hope that you can read my english.
> i am going to use rtlinux2.0-linux2.2.13. on embbeded pc
> ADVANTECH PCM-5820
> http://www.advantech.com/products/sbc/pcm-5820.htm
> it has a CyrixMediaGXm processor.
>
> a few days ago, i ran a small test program on this PC.
> the test is very simple, just null rt-task was runnig.
> rt_task_wait is 5ms. and this morning, linux was dead.
> (no keyboard response,no ping-answer,no ctrl-alt-del operation)
>
> i think this problem caused by these three reasons.
>
> 1) hardware trouble (over-heat? disk error?)
> 2) MediaGX's TSC trouble
> 3) gcc (2.95.2)
>
> i don't analize reason1.because normal-linux is very stable.
>
> MediaGXm has a TSC register.but linux-kernel disable this feature.
>
> /usr/src/linux-2.2.13/arch/i386/kerne/setup.c
> 676: else { /* MediaGX */
> 677: Cx86_cb[2] = (dir0_lsn & 1) ? '3' : '4';
> 678: p = Cx86_cb+2;
> 679: c->x86_model = (dir1 & 0x20) ? 1 : 2;
> 680: c->x86_capability&=~X86_FEATURE_TSC;
> 681: }
> the point is line 680,i don't know why he disables TSC.
>
> in the true,this processor has a TSC so i comment-out line 680
> and re-compile the kernel with gcc-2.95.2.
> then it become unstable.(i think MTBF is 24hour)
>
> i want your advice. what is my bad point ?
> thank you.
>
> ---
> yutarou ebihara [EMAIL PROTECTED]
> http://www.si-linux.org (SiliconLinux project)
>
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