For the people who might be searching for information about whether you can upgrade a T520 to 32GiB of memory:
Some T520 models come with CPUs that officially only support 16GiB of memory,
For example the i5-2520M:
http://ark.intel.com/products/52229/Int ... o-3_20-GHz
However some other models come with i7 CPUs that officially support 32GiB memory,
For example the i7-2670QM
http://ark.intel.com/products/53469/Int ... o-3_10-GHz
The T520 only has two SODIMM slots, and recently 16GiB SODIMM modules have become available,
and they aren't cheap, so I didn't just buy them to try them out, instead I went on looking up whether the
cpu will support these, and I believe the answer is NO.
The explanation is this:
An SODIMM can support per module:
- a maximum of 64 data bits
- a maximum of 2 ranks
- a maximum of 8 banks
- a maximum of 16 row addresses
- a number of column addresses
Column address bits 0..9 are transmitted on A0..A9.
The A10 line is used to transmit the Auto Precharge signal.
According to the JEDEC spec, if the memory has a C10 column, then it will have to be transmitted on the A11 address line.
So there is a hole in the mapping from column address bits to actual physical address lines, and it is conceivable,
that some memory controllers will not support driving the A11 line (and above) when specifying column addresses.
And that is exactly what's going on, the Intel 2nd generation i7 CPU memory controller is not able to drive the A11 signal correctly.
That means that this controller is not able to talk to SO-DIMM modules that are larger then 64 * 2 * 8 * 2^16 * 2^10 / 8 bytes =
8589934592 bytes = 8.0 GigaBytes
That being said, the W520 model should in theory be able to support 32GiB of memory with the right processor, and with 4x8GiB sticks,
because it has 4 SODIMM slots.
I have also found some hints on the internat that the 5th and 6th generation i7/i5 cpus support >=16GiB SODIMM modules,
but that this is unofficial, and intel doesn't support this usecase.
