> Since I can't seem to find a reasonably priced 68060-based system out there,

You do know that m68060 upgrades don't exist for Macs (I'm assuming you 
do...)

> I am looking at the CPU upgrade possibilities for 68k Macs. I have been 
> reading FAQs all over the place about upgrading Mac CPUs. I have read that 
> you can easily swap a 68LC040 out and put a 68040 in its place. I have not 
> found a clear answer on one thing though. Can I put a faster 68040 chip in 
> place of a slower 68LC040 chip? I just purchased an LC 575 motherboard for my 
> Color Classic (which now has a Color Classic II board in it) and I want to 
> replace its processor with a full 68040. It now has a 33 MHz 68LC040 and I 
> want to put in a 40 MHz 68040. Would that work? I am thinking it will not but 
> I am hoping it will. If that would work than I assume I could upgrade my 
> Quadra 650s to 40 MHz 68040 chips as well.

m68040 processors are often overclockable to 40 MHz. I've OC'd many, and 
I've never seen one that didn't work fine at 40 MHz.

You can swap out an LC m68040 for a full '040 in any system (although it'd 
be very hard to do that with a surface mount '040 in a PowerBook). The 
ROMs will be fine with the full '040.

As far as speed is concerned, yes, you can put in a faster chip, but the 
speed rating isn't really a big concern. It won't run any faster unless 
you make changes to the motherboard.

The 575s can be safely taken to 33 MHz:
http://homepage.mac.com/schrier/lc575.html

Quadra 650s and Quadra 800s can be taken to 40 MHz very easily by using 20 
MHz oscillators (less than $5 USD from many places online). Quadra 605s / 
LC475s can be taken to 33 MHz, like the LC575, by just moving surface 
mount resistors. They can also be taken to 40 MHz by using 20 MHz 
oscillators, but that's a little more work.

John Klos
-- 
Today is the day that my destiny calls me!
   Meowth