Hi Robert,
The ZIF processor upgrade I have in my Beige G3 MT (300 mHz originally) is a Sonnet G3/500--I wish it were a G4! I installed it when I still had OS9. It stayed in place when I installed Jaguar and, later, Panther.
As Grant mentions, I used a third-party helper program called
XPostFacto, "XPF" for short. Installing "unsupported" Panther with XPF was far easier than installing the "supported" Jaguar and the computer is now more stable.
T'was Grant who talked me into trying Panther. Now I can't believe I waited so long! I used an older version of XPF, version 3.1, at Grant's suggestion. V3.1 seems to be the "sweet spot" for installing Panther. Some Beige G3 owners have successfully installed 10.4.x with later version of XPF but more users have reported stability issues than with 10.3.
If you are interested in learning more about the upgrade paths available to the Beige G3, there is a very active forum area here:
http://discussions.apple.com/category.jspa?categoryID=110
Hope this helps!
A
