DETAILS
IBM designed the 8573 P75 series
"portables" to use processor cards,
similar in concept to some of the
other PS/2s that use processor
complexes. However, there was never an
upgrade card to improve on the
performance of P75 machines. What's
worse, the stock 486DX-33 processor
card was implemented without a
processor socket. What this means is
that the CPU was shipped soldered
directly to the processor card itself.
Here's a close-up look at the stock
486DX-33 CPU mounted on the processor
card:
Take special note of how the pins from
the processor go straight into the PCB
board itself and is soldered in place.
The following picture of the back side
of the processor card reveal the grid
of soldered CPU pins.
Well, a soldered-in CPU obviously does
not allow for much in improving the
processing power, so Jim took the
situation into his own hands with the
help of a Pace vacuum-powered
desoldering station. With steady
nerves and a lot of patience, Jim
actually removes the soldered-in
processor! With the processor off the
complex, there is a grid of 168 holes
where the processor once sat. So, the
final process in modifying the
processor card requires that a PGA
socket be soldered in to replace the
CPU, to which Jim says "your hand gets
awful damn tired" when you're done.
The end result can almost be thought
of as a masterpiece.
Here's how the processor card looks
once Jim has replaced the CPU with a
socket:
And here's the backside... Jim's
meticulous soldering makes the complex
look as factory as *before* the socket
mod:
Just to get a really good idea of how
clean of a job Jim does on the
desoldering, look at the resultant
holes left by where the processor pins
used to be.
The conversion of the processor card
to use a socket for the CPU allows for
some nifty upgrades. Jim has used both
the Intel DX4-100 Overdrive as well as
the AMD-133MHz processor on his
previous upgrades. Here's a picture of
the completed mod mounted with CPU
back into the P75 portable:
Of course, with a PGA socket in place,
there's always the possibility of
installing the popular Kingston
Turbochip as well:
My personal opinion on this mod is
"Wow..." (jaws dropped) and kudos to
Jim for exploring this territory. If
you've ever wondered whether upgrading
the P75's processor card could be
done, Jim has definitively laid that
question to rest.
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