Messages in this thread | | | Date | Wed, 03 Nov 1999 08:31:26 +0100 | From | Helge Hafting <> | Subject | Re: Perform minimal RAM test at boot |
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>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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