> > There is just one problem - some SIMM types return the same type code in
> > the register. So you have to try if the RAM really exists by accessing it.
> > If you try to access non existing RAM you'll get a NMI exception which
> > transfers control to the boot ROM ...
> Have you tried that? I doubt that it really works this way,
> since neither the hardware nor the BIOS can detect the
> difference between these SIMMs with identical IDs. The only
> way to find out what size of memory is installed is to
> access the last address of the expected memory area, and
> if a write-read-verify cycle fails, fall back to the smaller
> size. If the BIOS would get a NMI during this access, it
> couldn't determine the size either. Or have I missed something?
Yes, the BIOS recognises the NMI and use it to deciede if it has
just tried out writing to nonexisting RAM.