[U-Boot] AMCC 405EX Trap

[Wolfgang Denk]

In message <200905041708.59991.sr at denx.de> Stefan Roese wrote:
> On Monday 04 May 2009, Jonathan Haws wrote:
...
> > That is a good idea.  I haven't thought of performing those tests.  Are
> > there specific tests I can enable in the U-Boot environment for that?
> 
> Perhaps the memory tests from the POST infrastructure. But from my experience 
> a realworld application running under Linux is a good test. For example 
> compiling a Linux kernel in a loop. Perhaps mounted via NFS. Something like 
> this should fail at some time when SDRAM related problems exist.

Stefan is right. The memory tests in U-Boot all boil  down  to  plain
read-/write-cycles on the bus. This is nothing compared to the stress
you  put  on  the memory system when you have back-to-back burst mode
accesses. To get these, you need a combination of cache flushes (such
as in  an  OS  when  it  is  context-switching),  cache  loads  (like
instruction  fetches when lots of different code are being executed),
and DMA (like when you have heavy network traffic or  another  active
DMA  device).  Booting  Linux  with  root file system over NFS is the
easiest and one of the most reliable stress tests I know of.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
The following statement is not true.  The previous statement is true.