Jeff asks:
> My Vectra 486 -20 has an Intel 486SX-20 chip.
>
> Is it possible to replace this chip with a faster Intel chip without making
> any other changes, except software?
>
> If so, what speed is available, and what is the Intel part & hp part
> numbers, and approx. price?
>
> Any idea on where to get the part in the San Jose CA area?

I'd try looking into the Evergreen Technologies line of CPU replacements.

CDW is selling the low-end for $100 (http://www.cdw.com), according
to Price Watch (http://www.pricewatch.com, click on Processors,
then <Manfacturers : Evergreen Technologies>

I used one to replace a 486SX/25 successfully, although it didn't
have a great impact.

More than a CPU replacement, however, I'd encourage your father
to look at replacing the entire box ... for 400 to 600 you can get
a fairly powerful Pentium system (cpu, mem, disk, video card, etc)
without a monitor ... and probably have much better performance
and satisfaction!

Stan