[astrodust]

I recall one processor upgrade for a 1990-era Mac that slotted into the L2 cache slot, back when L2 cache was on the motherboard and used a similar DIMM format.

It was extremely unusual, but apparently worked.

[bcohen5055]

I had one of those... it was installed on a IICI, I think it was manufactured by sonnet tech and it was marketed as a PPC upgrade card for the motorolla 68040

Here is a list of all of the sonnect upgrade cards and how they connected http://www.everymac.com/upgrade_cards/sonnettech/

Edit: Added link

[astrodust]

Yeah, that was the one. I had a hard time tracking down the proper link, but it's on the page you linked: http://www.everymac.com/upgrade_cards/sonnettech/crescendo_g...

It's clever and insane at the same time. Most processor upgrades physically replace the processor, but this one just bypassed it.