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Subject: Re: Power On Self Test and testing memory
From: Pete Popov <ppopov@mvista.com>
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On Wed, 2003-05-14 at 15:26, Jeff Baitis wrote:
> Hi all:
> 
> I implemented memory tests in my bootloader code for the AU1500. I'm trying
> to figure out why Linux boots when loaded into cached KSEG0 (0x 80c0 0000),
> but my memory test FAILS for this same region.
> 
> (pretty backwards huh? get linux booting, then write memory tests!)
> 
> 
> I start by writing 0x5555 5555 to all of uncached memory, reading it back, and
> I write 0xAAAA AAAA to all of uncached memory and read it back.
> 
> This works great.
> 
> Next, I try to write 0x5555 5555 to cached KSEG0 memory, and it fails at addr
> 0x8000FE50. But Linux boots!

You're not overwriting any of the boot exception vectors, right?  What's
the failure exactly and how does the test work?

Pete

> I'm not issuing SYNC commands when writing to cached memory; could this be
> the problem?
> 
> We've exhaustively verified the memory burst parameters, etc. They look good.
> 
> Thank you in advance for your ideas!
> 
> Regards,
> Jeff