By referring to the pictures in this post: Can I connect an AT power supply to an XT motherboard? Why do these controllers (refer my 2nd post) have batteries?
I tested the first motherboard (with the 8088-2 CPU) and it wouldn't post. I haven't given up yet, but I suspect it could be a memory problem.
The second motherboard (with the NEC V20 12 MHz CPU) works fine.
I already swopped out the 8087-2 math co-processor from the other motherboard and it runs fine, but I'm a bit worried in terms of the different speed ratings.

Since the NEC V20 is running at 12 MHz (although, I can slow it down via the turbo switch to 4.77 MHz) and the 8088-2 is rated to run at 8 MHz, can I swop out the 8088-2 CPU and install it on the second (smaller sized) motherboard that the NEC V20 is running in?
Is there anything I should watch out for and/or check before attempting this swop.