These L2 caches were available in different sizes and can be the same size as

the RAM in these Macs but only up to 1MB were produced.

pinout lists them as SIMM:

http://support.apple.com/kb/TA34395?viewlocale=en_US

Its a real speedup on a 6100 and can even buffer the onboard video that runs

on the slow system RAM.A lot of old computers have L2 cache installed but on a 6100/60 its the opposite.