MPC755 L2 Cache data parity error

[Chris Zimman]

On Sun, Jun 15, 2003 at 11:06:38PM +0800, Shenrong wrote:
> size to 512k or 256k, but don't know why. We use both the PBGA and
> CBGA packages, seems CBGA version are some more stable(still has problem),
> don't know why too.

The first thing I thought of when I read this is heat issues -- especially because
of the mention of PBGA vs. CBGA.  Is your heat sinking/cooling adequate?

I had a problem once with a custom 405GP board that was not entirely dissimilar.
Running the OpenSSL 'speed' benchmark, the system would lock up doing the MD2 tests.
I couldn't fathom how a userland program could lockup the entire system.  One day,
just by chance, I happened to stand the board on end -- no more crashes.  The
difference had been the airflow underneath the device because it didn't have a
heatsink on it.  Consequently, I put a heatsink on the 405 and that fixed the
problem altogether.

>    It's more strange that I can simply let the error occur under Linux with
> continuous file copying in ram disk. But I can't let it occur under PPCBoot
> with whatever memory operations for even one time, whether use the L2 Cache
> memory as L2 Cache or as private memory. The L2 Cache has the same setting
> in the above two circumstances.

The only difference I could think of right away here is that under
Linux, you're doing burst reads and writes.

--Chris

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