Re: Athlon: Try this (was: Re: Athlon bug stomping #2)

Jonathan Morton (
Sat, 15 Sep 2001 19:02:37 +0100

> > > +static void __init pci_fixup_athlon_bug(struct pci_dev *d)
>> > +{
>> > + u8 v;
>> > + pci_read_config_byte(d, 0x55, &v);
>> > + if(v & 0x80) {
>> > + printk(KERN_NOTICE "Stomping on Athlon bug.\n");
>> > + v &= 0x7f; /* clear bit 55.7 */
>> > + pci_write_config_byte(d, 0x55, v);
>> > + }
>> > +}
>> >
>> > Well, these are cosmetic changes anyway...
>> > What is more important now:
>> > 1) Do we have people who still see Athlon bug with the patch?
>> > 2) Do Alan read these messages? ;-)
>> Im watching the discussion with interest. If it proves to be the magic
>> bullet I will ask VIA for guidance on the issue
>Not being a developer or guru on the internal software workings of the
>hardware here, I have to ask, does this clear up some bug, or does it
>disable the optimizations causing the problem? Is this a *fix* or a

AFAICT, it's a *fix*. The register in question is "for debug use
only, never write anything other than zero in it" but generally shows
non-zero when a faulty BIOS is installed. We're zeroing the bit that
appears to cause the problem. It's highly unlikely to be an extra
optimisation - if it is, it's an unsafe one.

from:     Jonathan "Chromatix" Morton
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