Thinkpads Forum

There are different i7 processors on same G2 socket that takes 16GB or 32GB max
For example:

dual core i7-2620M is 16GB dual channel; 1066/1333 fsb. 35W
quad core i7-2820QM is 32GB dual channel; 1066/1333/1600 fsb. 45W
note: these wattage is TDP, dual channel means two slot memory usually and all are DDR3 type.

Cheers, thinkpadcollection

Correct, only the quad core I7 processors can take 32GB ram, dual cores cannot. This is why you see 'dummy' slots in non QC W520 models, for example. There will be 4 slots, but 2 of the slots under the keyboard will have 'dummy' sticks in them. Putting ram here will not allow the computer to boot.

While some of these CPUs themselves are capable of addressing 32GB of RAM, they are only able to do so in the 4-slot environment of the W520.

There are no DIMMs larger than 8GB that will work in these machines.