I shouldn't be responding to this (I've transferred my
subscription to my home computer) but couldn't resist.
I think the base(A) was 64K and the max(B) was 640K,
apparently because some decision maker didn't understand
the value of powers of 2. Sorry but supporting materials
are not at hand, but I think I can back this up.
(A: Motherboard, B: A+Bus cards)
John A.