On Sat, Oct 17, 1998 at 05:23:56PM +0200, Michael Mess wrote:
[snip]
> 2) A workaround about this problem would be a memory-check if the bios
> reports 64MB RAM. The memory check can detect more RAM if there is more.
>
> We could check memory by writing some bytes ( hexadecimal values FF, AA,
> 55, 00 ) into each byte at addresses above 64MB RAM and then reading and
> comparing. If these addresses contain memory, these bytes will be stored
> and the comparison will be successfull.
> If we enter adresses without memory the values written will be lost and
> we will read some garbage, so the comparison will fail.
> Thus we can detect the right memory_end.
>
This is correct unless you have a braindamaged motherboard that will fail to
report errors after the suported amount of ram. So if you do this in a
motherboard limited to 128M (example) and the memory controler is stupid at
128M+1 you will write in position 0x1. Not good.
I don't know if there is such a motherboard out there but it's a real
hazard.
> Maybe there are some difficulties as the processor uses cache so we have
> to prevent that we read back only from processor-cache.
>
Caches can be dealt with. That is the least of our problems :)
cheers
- --
Carlos Morgado - l39801@alfa.ist.utl.pt - http://alfa.ist.utl.pt/~c39801
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