Some planning is required if you want to migrate a Wallstreet SO-DIMM RAM module to the new Lombard machines. Most SO-DIMMs purchased for Wallstreet are the 2.0 inch form factor, which means that they are only compatible with the upper (larger) RAM slot in Lombard.

This means that if you upgrade from Wallstreet to Lombard and move your 128 MB RAM module to it, you will not be able to max it out to 384 MB. Acccording to page 69 of the Lombard Developer’s note you have to purchase a 1.5 inch 128 MB and a 2.0 inch 256 MB module to max it out to 384 MB:

An SO-DIMM using presently-available parts can contain either 16, 32, 64, 128, or 256 MB of memory. Because of space limitations, a 256 MB SO-DIMM will fit only in the top slot.

Total RAM capacity using the highest-density devices available is 384 MB and is limited by the space available for the SO-DIMMs. The bottom slot can accommodate a 1.5-inch SO-DIMM with up to 128 MB of SDRAM. The top slot can accommodate a 2.0-inch SO-DIMM with up to 256 MB of SDRAM.