More RAM for my 7300

[Mark A. Fleming]

wet!editor at cca.ucsf.edu (Eric Swnason) writes:


> I recently obtained a Unix-PC 7300 -- stock, as nearly as I can tell.
> 20 meg slower-than-Christmas hard drive, half a meg RAM, and so on.
> I'm interested (of course) in upgrading the memory.  What are my
> options?  I know I can get a memory upgrade board, but I don't know
> where or what it might cost.
> 
> My first inclination, if possible, would be to play some trick on the
> motherboard -- is there some way to replace the existing memory with
> higher-density chips or do one of those chip-piggybacking tricks?
> 
> I await proposals from the peanut gallery.  Please don't delay; I'm
> sure I'll run up against the half-meg wall soon, and in a big way.

     I've searched around without success for the original instructions
on how to upgrade the motherboard memory from .5M to 2M.  These were
posted to the net about two years ago.  Does anyone have a copy, or
remember who the author was?  Please help, as I'm sure there are others
who would appreciate this information.  It should certainly be archived
at osu-cis.

     Working from memory, I recall that you must first remove the 64K
chips from the motherboard.  The RAM is located in the upper right hand
corner of the motherboard, 8 rows of 9 chips.  Use a pair of clips to cut
the legs off of the RAM chips.  Now, with a low watt iron and a solder
sucker, remove the solder from around the RAM pins and pull the pins.
Install 72 16-pin sockets, so you'll never have to go through this again :-).
The chips are packed pretty close togeather, so you need the narrow ones,
or some single inline sockets.  Insert 72 4256 RAM chips, the 150ns versions.
Change jumper J1 from E2-E3 to E2-E1.  This jumper is located at the front
of the motherboard, near the left hand corner of the memory array.  The
jumper setting is via a circuit trace, so you'll have to cut the trace
and install a wire between E2 and E1.  If all your solder joints are clean,
and you haven't lifted any traces, you should boot up with 2M of RAM.

     Supposedly, this same process could be applied to the .5M RAM
expansion board which the jumbo (1M RAM, 20M HD) 7300's came with.
For years, I've been planning to do this to my own 7300 when time and
money permitted.  If anyone can track down the original instructions and
repost them, it would be of great service to those who own one of the
earlier model 7300's.

Thanks.

Mark Fleming    calvin!mark at ncoast.ORG
                usenet.ins.cwru.edu!ncoast!calvin!mark