Max. RAM Capasity for X40 1024 or 1536 ?

[ThinkPadX40]

my x40 features sas max ram capasity 1 GB (1024 MB)

But in the IBM upgrade page it seems 1536 MB nonparity RAM is possible

What does it mean?

[sdaniels]

if your X40 came with 256 MB of RAM, then the max RAM capacity is 256+1024 = 1280. If your X40 came with 512 MB of RAM, then the max RAM capacity is 512 + 1024 = 1536. The base amount of RAM (256 or 512) is soldered to the motherboard and cannot be changed/removed, but there is a single SO-DIMM slot available for adding RAM to the base amount.