Peter Horton <pdh@colonel-panic.com> writes:

> I've found the cause of silent disk corruption on my A7V motherboard,
> and it might affect all boards with the same North bridge (KT133 etc).
> 
> For some reason the IDE controller(s) was sometimes picking up stale
> data during bus master DMA to the drive. Assuming that there was no bug
> in the CPU it had to be the North bridge that was caching the stuff when
> it shouldn't have been. I assume the problem would also apply to other
> bus masters (SCSI, NIC etc).
> 
> Scanning the motherboard manual showed up a chipset setting "PCI master
> read caching" which I suspect is the culprit. According to the manual
> this defaults to "on" for Athlons and "off" for Durons (obviously other
> BIOSes / MB might treat this setting differently). Unfortunately my BIOS
> does not allow me to change this setting independently [1], I only have
> the choice of running the machine in "normal" or "optimal" configuration
> to alter this setting ("optimal" is the default).
> 
> In "normal" mode my machine is rock solid and I see no corruption,
> however "normal" mode also changes a lot of other settings (AGP speed,
> DRAM interleave etc). Anyone experiencing such corruption should look
> for a BIOS setting which disables this "feature".
> 
> If anyone out there has a BIOS which allows them to change just this one
> setting can they diff the "lspci -vvxxx" output with the setting off and
> then on so we can isolate which host bridge biti(s) control this feature.
> Maybe we can then add it to 'pci_quirks' and reduce the number of VIA
> corruption reports.

It seem I have such an options,
named K7 CLK_CTL, under Advanced Setting, with two possible
choise : Optimal or Default.

Here is the output of lspci with each of them,
I hope it will help.