Re: i686 quirk for AMD Geode

Ingo Molnar
2009-10-03T07:21:31Z

* Matteo Croce <technoboy85@gmail.com> wrote:

> Hi,
>
> the AMD GEode LX has an x86 id of 5 (i586) tought it's technically an i686:
>
> root@alix:/usr/src# cat /proc/cpuinfo
> processor : 0
> vendor_id : AuthenticAMD
> cpu family : 5
> model : 10
> model name : Geode(TM) Integrated Processor by AMD PCS
> stepping : 2
> cpu MHz : 498.060
> cache size : 128 KB
> fdiv_bug : no
> hlt_bug : no
> f00f_bug : no
> coma_bug : no
> fpu : yes
> fpu_exception : yes
> cpuid level : 1
> wp : yes
> flags : fpu de pse tsc msr cx8 sep pge cmov clflush mmx
> mmxext 3dnowext 3dnow
> bogomips : 996.12
> clflush size : 32
> cache_alignment : 32
> address sizes : 32 bits physical, 32 bits virtual
> power management:
>
> indeed it has mmx, mmxext and cmov.
> So I added the quirk below and I can confirm that the system is running fine.
> I did an x264 encode to trigger any SIGILL due to missing opcodes, but
> it worked.
>
> I also did this simple test which gives a ~2.5x speed boost:
> http://pastebin.ca/1590089
>
> I wish some feedback from someone, I really dunno why AMD set the
> cpuid value to 5
>
> --- a/arch/x86/kernel/cpu/bugs.c 2009-10-03 03:43:02.399323313 +0200
> +++ b/arch/x86/kernel/cpu/bugs.c 2009-10-03 03:54:22.582205090 +0200
> @@ -151,6 +151,12 @@
> #endif
> }
>
> +static void __init check_geode_i586(void)
> +{
> + if(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
> + boot_cpu_data.x86_model == 10 && boot_cpu_data.x86 == 5)
> + boot_cpu_data.x86 = 6;
> +}
>
> void __init check_bugs(void)
> {
> @@ -163,6 +169,7 @@
> check_fpu();
> check_hlt();
> check_popad();
> + check_geode_i586();
> init_utsname()->machine[1] =
> '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
> alternative_instructions();

Looks good, but your signoff line is missing.

Ingo