How do you remap memory on a 386 ?

[ilan343 at violet.berkeley.edu]

In article <[252da3cc:205.1]comp.unix.i386;1 at tronsbox.UUCP> tron1 at tronsbox.UUCP (HIM) writes:
>>	I've just bought a 386 machine with 1Mb RAM and intend to run UNIX on it. 
>>	One thing strikes me as odd -  only 640kb of memory is visible.
>
>Not Odd at all. 
>
>*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.
>
>You might as well shadow and get the speed.
>
>ALL the UNIX systems I have installed have this problem.
>
I thought that was the case for most 386 boxes. However, I just
installed 386/ix in a system built around a DTK 20MHz motherboard, with
5MB of RAM installed.

I dont't think I have a shadow RAM option. Upon booting-up, the DTK
BIOS test gives me

Base memory 640KB, Extended RAM 4480 KB (Total 5120 KB)
 I concluded  that the RAM between 640 and 1M is being remapped to
 Extended memory addresses.

 When UNIX boots-up, all of the memory seems to be there, it gives me
 5242880 bytes total.


What is happening with other motherboards. Do you have an option of
disabling shadow ram and remapping the memory above 640K?