ac100 team mailing list archive

[Gordan Bobic <gordan@xxxxxxxxxx>]

On Fri, 19 Aug 2011 15:55:57 +0200, Marc Dietrich <marvin24@xxxxxx> 
wrote:
> Hi Gordan,
>
> Am Freitag 19 August 2011, 11:18:31 schrieb Gordan Bobic:
> >  As some of you may have already heard on the IRC channel, I had my
> >  AC100 suddenly become very unstable under load. When doing big 
> > compile
> > [...]
> >  My gut feeling at the moment is that the RAM could be over-timed so 
> > I'm
> >  going to try modifying the kernel code to relax the RAM timings by 
> > a
> >  notch.
>
> we are not touching RAM timings so far on kernel 2.6.38. It may be
> possible that the original kernels does so.

Well, my plan was to up the timings in 
arch/arm/mach-tegra/board-paz00-memory.c. Can you confirm whether the 
values there are in units of clock cycles? Or is it ns? Also which line 
corresponds to CAS? I can see RAS, RC, RCD, RRD, RFC, but can't see a 
value for CAS, which is, at least in theory, the most imporant one.

> >  The only competing idea is that Tegra2 comes pre-overclocked past 
> > the
> >  stable limits for 100% load for prolonged periods. This wouldn't
> >  surprise me either (Nvidia chips have proven unreliable in the past 
> > even
> >  at their default clock speeds, both the motherboard chipsets and 
> > GPUs),
> >  but I would like to think that Toshiba would have done some due
> >  dilligence testing of their product. For comparison, my SheevaPlug 
> > is
> >  compiling 24/7 for weeks at a time and has never errored out.
>
> It could also be related to power supply. What we do is modifing the 
> voltage
> supplies for serveral power sources. I had the feeling, that Toshiba
> undervoltaged some CPU supplies in order to save energy (compared to 
> other
> boards). So I increased SM1 from 1V to 1.2V which may have been 
> wrong.

How did you do this?

> It would be nice if you could test a .32 based kernel and see if it
> also happens there. Also you could try your new model.

I haven't tried 2.6.32 because I couldn't find one at the time, but I 
tried the old 2.6.29 and 2.6.38, and the instability on my old AC100 was 
the same. Haven't tried it on the new one yet. Do you think 2.6.32 could 
be behaving differently to both of those? If so, why? Where can I get 
the Tegra-patched 2.6.32 kernel?

> Finially, it could also be possible that this is a design bug, which
> may be hard to solve for us.

Plausible. At the moment, though, I'm most interested in finding out 
whether other people are seeing similar issues under prolonged load. It 
would also be useful to establish whether this might be specific to the 
RAM chips used (e.g. Micron chips erroring, but Hynix being OK)

Gordan