Here's a question that may be simple enough to answer, but has stumped
myself and a few others:

What does an external RAM cache card do for you if you already have a large
cache set (through control panel) in your SIMMs?

EX:  I have a Mac IIci with 20 meg RAM, an external video card (so I don't
rob my SIMM's), and the default Apple cache card (I believe this is 32K?). 
Say I have my cache set at 2 MEG, what good does a measly 32K do me on the
cache card?  Could it actually slow things down by dividing the cache
between the card and the SIMM's?  Or does it still speed things up by
providing a 'secondary staging' area for data normally passed directly into
the SIMM RAM cache?

I'm confused because it seems like cache cards are so low in memory to
really do any good compared to what you can set yourself.  Yet, Daystar
FastCache has numbers which show around a 30% performance boost on some
operations.  Are the chips on the cache card simply faster than most SIMM
accesses?

Please help, I'm trying to find the optimum memory settings for the IIci
system described in the EX above.