How do you remap memory on a 386 ?

[Piercarlo Grandi]

In article <[252da3cc:205.1]comp.unix.i386;1 at tronsbox.UUCP> tron1 at tronsbox.UUCP (HIM) writes:
    
    *0386 (and in fact AT's) use the address space from 640-1MEG as the space
    for various ROMS for VGA , HD CONTROLLERS and the like.
    
    As far as I know , there is NO way to get it into useful space.

Not entirely true. Most of these machines actually remap the missing 384k to
high memory; you can disable shadowing, and the 384k will reappear at some
high address. With Unix 3.2 you can specify in /etc/default/boot which
regions of memory the kernel will look at at boot time to search for
physical memory; these regions need not be contiguous at all.

Most Unix 3.2 systems come with a selection of examples of this for various
types of machines. have a look at the /etc/default directory, and the
boot(1M) manual page, and the CPU manual for your machine to know how to
disable shadowing.

Some (very few) machines (e.g., I think, but not sure, Dell) don't remap the
384k into any really accessible part of the physical address space. Too
bad...
-- 
Piercarlo "Peter" Grandi           | ARPA: pcg%cs.aber.ac.uk at nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcvax!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg at cs.aber.ac.uk