Messages in this thread | | | Date | Wed, 3 Nov 1999 15:38:53 +0100 | From | Jan Echternach <> | Subject | Re: Perform minimal RAM test at boot |
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On Wed, Nov 03, 1999 at 08:31:26AM +0100, Helge Hafting wrote: > Also note that a non-destructive test is possible. The commodore 64 had > that. > It tested by reading a byte, invert and write it back, test, invert and > write > back again.
IIRC it used a slightly different method: Read byte, write 0x55 and test, write 0xaa and test, write back old byte.
> This preserves data in all cases (except if the test
It destroyed one byte of RAM at address 0xa000, because reading 0xa000 read the 1st byte of the Basic ROM, whereas writing 0xa000 wrote the 40961st byte of RAM.
However, this doesn't matter for the linux kernel because all tested memory is supposed to be normal RAM, and the test is only a sanity check.
I think the kernel should print a message and halt immediately after the first address that failed the test, because at that point the kernel has already made an invalid memory access.
-- Jan
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