Achieving maximum expansion memory without 2MB Card, How??

[flinton at eagle.wesleyan.edu]

In article <553 at alfred.UUCP>, elliot at alfred.UUCP (Elliot Dierksen) writes:
 
> I have a 3B1 (used to be a 7300 before I hacked it to bits!!) that currently
> has 3.5MB of RAM.  I have a 512K RAM card & a 1MB Combo card currently
> installed. My question is: If I fully populate the Combo card, am I going to
> be able to get to that 4MB point or is that 512K that I add just going to
> step on the 512K card.  I thought I had heard something about being able to
> path the cards so they would run correctly.
> 
> If it's not possible, please let me know.  I would hate to have a 512K
> paperweight and still only 3.5MB. Any assistance/comments is greatly
> appreciated..  Thanx,

In the First Edition (November 1986) of the "S/50 Reference Manual" -- aka
the UNIX(r) PC Reference Manual -- page 7 of Appendix C (Expansion Memory
Locations) clearly suggests that the _only_ way to achieve 4.0 Meg is
with 2.0 Meg on the CPU board and a fully populated 2.0 Meg RAM card in any
slot.

If someone knows a hardware mod with which to overcome this -- or better still
a hardware mod to utilize all 24 RAM address lines (instead of the 22 actually
used -- see above-mentioned Ref. Man. Chapter 2 pages 2-2 and 2-3) -- there'll
surely be wide interest in seeing such info posted.

-- fejlinton