z-Re: memory detection and bios
Peter P. Eiserloh (eiserloh@llab.chinalake.navy.mil)
Tue, 22 Oct 1996 13:04:35 -0700
> > bios can only report 64Meg. Is there a reason the kernel can't do
> > a search for the memory boundary if 64Meg is available? [e.g. check
> > at 128M, 256M, ... then binary search for boundary when get a miss --
> > maybe do something quick and simple to check for a proper boundary like
> > check the location immediately past the last known good location.]
> >
> > If this causes problems on some machines it could be made a config option.
> >
> > For people whose bioses report the wrong value, this could be made
> > "always on" instead of "only if 64M reported".
>
> What if you have a memory mapped device or frame buffer at 128MB. Memory
> probes
> can be quite dangerous with some hardware (the probe tells your
> memory mapped scsi controler to format the drive..)
>
> Just add mem=XXXM to the kernel boot options (e.g. append option in
> lilo.conf) and all will be well.
Thats what "make config" is for, so a custom kernel can be built which
does what the super-user wants. If CONFIG_64M_PROBE is defined then the
kernel should probe for memory greater than 64Meg when the bois reports
exactly 64Meg. If CONFIG_NEW_BIOS_MEM is defined always use the new bios
calls to get the correct memory configuration. If these are not defined
then use the current mechanization (mem=xxxM). This allows a kernel to be
built which can automatically test for the correct memory layout if it is
run on a newwer mother board. These config options would fail with older
mother boards (possibly catastophically), but that is what "make config" is
all about!
Peter
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