The 5000/200 and 5000/240 _hardware_ supports mixing memory sizes.
NetBSD doesn't, quite: you get the first contiguous chunk,
which in this case is the 32meg modules and the first 8meg module.

With UVM we can add support for mixed memory sizes easily enough.  I
was hoping to add it and test it with a 3MIN, but the darn PROM is
unhappy if I add any pairs of 2meg SIMMs to the pairs-of-8meg config.