MMU problems?

Patrick Lerda Lerda at
Fri Jun 23 18:06:19 EST 2000

I've now  a success with our board. It takes hours to compile with our
kernel configuration file,
on a NFS mounted partition, a PPC823 board with 64MB of memory.

Patrick LERDA

> -----Message d'origine-----
> De:	Wolfgang Denk [SMTP:wd at]
> Date:	jeudi 22 juin 2000 19:25
> À:	Lucinda Schafer
> Cc:	Patrick Lerda; 'Dan Malek'; Nguyen Xuan Hoang;
> linuxppc-embedded at
> Objet:	Re: MMU problems?
> In message
> <A109131318C4D1119AC20060088DECE330F4B1 at> you
> wrote:
> >
> > I agree. I believe we ARE dealing with a kernel bug, and it is
> particular to
> > the MPC823.
> What makes you think so? Have you run the same  hardware  with  other
> CPUs  without  problems?  Have  you  seen  other  "good" hardware (TQ
> Components, Embedded Planet) having with similar problems,  and  only
> when running with 823 CPUs?
> > Let's hear some success stories--embedded units in production, running
> in
> > the field for days, shutting down power and rebooting with no kernel
> panics.
> > That may help convince me we are dealing with a hardware issue.
> OK, then here is a success story.
> I have several systems in test here, a mix of 823, 850, 860, -DE, -T,
> -SR, and  some  development  systems  are  in  permanent  use  by  my
> customers, and I can't say I see any differences between the CPU's.
> Booting or shutting down was _never_ a  problem.  We  had  the  usual
> crashes  whith  early  versions of 2.2.13 when running low on memory,
> but that's fixed.
> With recent kernels (for instance, the  2.2.13  version  from  MV)  I
> haven't  problems  for  a _very_ long time (except for the 2.4.0 test
> kernels - but I don't use these in production yet).
> Did you check if environmental parameters make  any  difference?  How
> stable  is  your power supply - are the voltages for your board clean
> and within limits?
> Did you measure CPU temperatures, or did you try cooling the CPU's? I
> remember early versions of some TQ modules  (MPC821  +  Adaptec  SCSI
> controller  on  a  credit  card  sized modules) which got too hot and
> stopped working.
> And yes, I just compiled (once more) a Linux  kernel  on  one  of  my
> boxes  (that's  why  I reply so late - it takes more than 140 minutes
> with a NFS based root filsystem and 16 MB of RAM). You are right,  it
> makes  kind  of  a good regression test - it streeses all of CPU, I/O
> and (with NFS root) networking.
> You asked for success stories: It works for me.
> Wolfgang Denk
> --
> Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
> Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at
> "Virtual" means never knowing where your next byte is coming from.

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