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SubjectRe: Possible critical VIA vt82c686a chip bug (private question)
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Vojtech Pavlik <vojtech@suse.cz> writes:

> On Thu, Oct 26, 2000 at 04:42:31PM +0200, Yoann Vandoorselaere wrote:
>
> > > On Thu, Oct 26, 2000 at 04:20:43PM +0200, Yoann Vandoorselaere wrote:
> > >
> > > > ...
> > > >
> > > > Have you any idea what is the relation between time and this chip ?
> > > >
> > > > Also, I'm experiencing the problem for several month on my
> > > > workstation and I never could find where it was comming from...
> > > > how did you do ?
> > >
> > > Well, it integrates both the i8253 PIT and the vt82c586 IDE controller.
> > >
> > > I first located the wrong time was coming from gettimeofday() and not
> > > from the other sources of time the kernel provides. And then I was
> > > tracking the problem (which actually is an underflow - the chip bug
> > > causes some time offset variables go negative - 0xffffffff microseconds
> > > is about 1:20 hours). And this way I got to the spot where the patch
> > > cures the problem.
> >
> > Ok, here is what I experienced :
> >
> > First what is strange is that :
> > - I'm using SCSI
> > - I just have an IDE disk for mp3.
> > The IDE subsystem is never used heavilly...
> >
> > I've experienced the problem after some time of
> > heavy scsi IO, my screen under X was going black (like with dpms)
> > When I was moving the mouse, the image was coming back
> > for < 1 seconds, then black screen...
> >
> > The only fix was to kill X then to reboot.
> >
> > Anyway, thanks for your explaination...
> > I'll do a feedback for this patch ASAP.
>
> Interesting. If it's caused by SCSI as well (might be), then it's not
> caused by heavy IDE activity but rather than that it could be heavy
> BusMastering activity instead (The IDE chip does BM as well).
>
> I'm still wondering if it could be a Linux kernel bug (bad/concurrent
> accesses to the i8253 registers), this has to be checked.

An easy way to verify the problem is to start 'dbench 128',
I'm gonna do that with and without IDE subsystem to see what
happen.

--
-- Yoann http://www.mandrakesoft.com/~yoann/
I worry about my child and the Internet all the time, even though she's too
young to have logged on yet. Here's what I worry about. I worry that 10 or 15
years from now, she will come to me and say 'Daddy, where were you when they
took freedom of the press away from the Internet?' -- Mike Godwin
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