[SunRescue] CPU switching

[James Lockwood]

On Thu, 16 Sep 1999, Bjrn Ramqvist wrote:

> Speaking of soldering...
> I have this nice SS5/110 motherboard that is broken and I was thinking,
> is it even close to possible, by hand, to solder off the CPU?
> I have a SS5/70 with a socketed processor and it would be happy with
> some more horsepower. :-)

It's possible if you're careful.  You'll fry the old motherboard though.

The best way of all to do it is to get one of those big screw-type chip
pullers used for socketed PGA chips.  Clamp it to the 110MHz CPU and turn
the handle until you are _gently_ applying force.  Then take a small
butane pocket-torch and fan it rapidly over the back of the board behind
the CPU.  Once the solder melts the tension on the tool will "pop" it out
a millimeter or two, and then you can easily remove it.  The tool will
also help keep the CPU cool as the arms that clamp onto it are usually
aluminum.

Keep in mind that to transplant it to the new board you will not only have
to set jumpers but also swap out the CPU clock oscillator.  Compare the
two boards and swap the one that is different, also try to mimic the
jumper settings.

Note that the probability is at least 50% that the fault in the SS5/110 is
the CPU itself, so you might end up doing all this work for nothing.  At
the very least, socket the oscillator so you can easily go back.

Consider trying to find a Fujitsu 160MHz TurboSPARC upgrade instead.  That
will plug directly into your socket (and you have to upgrade the boot PROM
as well).

-James