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SubjectRe: Perform minimal RAM test at boot
>Also, don't expect it to detect anything reliable (think of a video
>card in the 15-16M memory hole.)

Timing the memory accesses will probably detect things like that, as
PCI/AGP tend to be slower than ordinary memory. We could get
a warning about slow ram at least, this would also warn about those
motherboards that don't cache everything.

> Note also that
> the only way to test for memory's presence is to write to it & try to read
> back. This destroys any data which might have been put there by the
> bios.........

This test only mess with memory that would be mapped by the kernel
anyway, so
nothing to worry about. Getting a crash during boot is certainly better
than
mysterious corruption some time later.

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. This preserves data in all cases (except if the test
routine
tests its own instruction memory, as I discovered :-). And it cannot be
fooled by the uncommon but possible scenario of ROM that happens to
contain the exact test pattern you use.

Helge Hafting

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