Can a CPU with a 256K L2 cache be used in a motherboard with a 512K L2
cache without damage to either component?

Specifically, I would like to use a Intel P4 2.0/256/400/1.75 SL5TL in
a Intel D8656PERL motherboard which has a 512 L2 cache.

It appears that the motherboard you have listed may possibly be listed
incorrectly as i found not results using the model # you have in your
question. Commonly, the only necessary requirement for compatability
between motherboard and processor is the Socket type, not cahce size,
as only OLDER pentium I and II mobos used an on baord cache
compatability variable.

The Pent 4 2ghz 256l2 cached 400mhz frontside bus 1.75v processor is a
socket 478 FC-PGA2 or Flip-Chip, this chip will work in any socket 478
mother board that supports a 400mhz Front-Side bus speed.

Z