It is not a BIOS trick. The extra 128K appears in the upper memory area,
from D000 to EFFF. There was a special device driver
available, USE!UMBS.SYS,
that turned this memory into UMB's if you were running
DOS 5. Great for
parking mouse and network drivers in. The driver was written by a hobbyist
as a memory study project, it was available with the machine code source
so you could modify it for other computers. IIRC it should be on Simtel.
I also have a copy around here somewhere. I used to admin a network that
had lots of Philips XTs, NMS9100 and P3105 were the ones that had this
extra memory.
Kees
--
Kees Stravers - Geldrop, The Netherlands - pb0aia at amsat dot org
Sysadmin and DEC PDP/VAX preservationist -
http://vaxarchive.ml.org
Net-Tamer V 1.08.1 - Registered