1M to 2M revisited...

[Michael Ditto]

In article <8570002 at eecs.nwu.edu> morrison at eecs.nwu.edu (Vance Morrison) writes:
>I have some friendly advice for those interested in upgrading the
>motherboard ram.  It is not as easy as plugging in the ram chips.
  [ ... lists some other things that are required ... ]

Then, in <574 at bacchus.UUCP> darren at bacchus.UUCP (Darren Friedlein) writes:
>I've done all this (4 multiplexers, all the chips, a capacitor on each
>chip, the resitor packs and set the jumpers like I was told (same as
>1M in 4 banks).  Still doesn't work.  Anyone know what's missing?

I've upgraded a 1Meg 7300 to 2Meg, so I know it's possible.  I didn't
have to change the jumpers, since they specify chip size (64K vs. 256K).
I DID have to cut two traces and jumper them somewhere else.
Unfortunately, I didn't write down what the changes were, and I don't
have my hardware manual handy; but they were related to address decoding
and selecting one bank vs. the other.  I'll try to get the details and
post them soon.

I feel guilty about posting this teaser ("I've done it, but I'm not
gonna tell you how, nyah nyah" :-) because I did exactly the same thing
about 5 months ago.  The thing I was waiting for then was to make the
same mod to a second machine and take careful notes so that I could tell
you all about it.  Well, I never got around to it (and no longer have
access to that 7300 or the one I hacked), so I'll have to study the
schematics again and hopefully I'll remember the exact mod; at the least
I should be able to give some pointers.

Good luck, hardware hackers!

-- 
					-=] Ford [=-

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