[coreboot] How to test RAM beyond 640 kByte boundary

Peter Stuge peter at stuge.se
Wed May 21 12:31:24 CEST 2008

On Wed, May 21, 2008 at 11:57:02AM +0200, llandre wrote:
> I have a question about the ram_check function.
> All the board specific codes invoke it like this:
> ram_check(0x00000000, 640 * 1024);
> I had a look with JTAG debugger and indeed the RAM beyond 640 KByte
> boundary is not accessible. Why? Is it possible to enable and test
> all the RAM available?

I would like to remove this function from our codebase.

Please note that this is not a useful RAM test.

Please build coreboot with a memtest86 payload in order to test your
RAM setup.

ram_check() is ONLY useful for _very early_ testing of the RAM setup.

Even successful ram_check() does not indicate that RAM is completely
correctly set up. You have to run a burn-in test like memtest86 for
a long time to have reliable results.


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