If so, the lack of address lines to the memory slots and how the BX chipset boards uses two CAS lines to get 256M of memory in a slot AKA "double-sided" makes the common off the shelf memory show up as 128 megabytes.

Crucial.com usually gets it right and supplies the proper sticks and tells you how much of what type you can put in the machines.

Or you read the motherboard manual.