W520 Quad Core upgrading to 16GB Memory

[eecon]

Which would be preferable from a stability or performance basis for 16GB .... Four 4GB or two 8GB modules?

I received my W520 i7-2860QM with one Lenovo 4GB PC-10600 1333MHz module and would like to go to 16GB.

I happen to have a new Crucial 2x4GB kit of PC-10600 1333MHz CL9 1.35V modules that I bought for my T500 that I may not need to use as I think I may sell the T500.

Should I just buy one more matching true Lenovo 4GB PC-10600 module (FRU 55Y3711 / 55Y3717) directly from Lenovo for about $40 and go with all four slots filled with 4GB modules (placed in the proper slots per the odd-ball mapping instructions so the two matching Lenovo modules are in 0 and 1 and the Crucials from the 2x4GB kit are in 2 and 3).

Not sure if the Lenovo modules are CL9 (I think they are though) but they are 1.5V whereas the Crucial modules are CL9 and 1.35V (but I think they will run at 1.5V if a system does not support 1.35V modules).

For about $70 I can get a Crucial or Corsair 2x8GB kit of PC-10600 1333GHz modules and just leave two slots open.

Which is the theoretically preferred approach here (w/o regard to cost or future expandability)?

Thank you

[wolfman]

You can check out the existing Lenovo module's CAS rating using CPU-Z (http://www.cpuid.com/softwares/cpu-z.html). Matching pairs of RAM are theoretically best, so getting a 4gb stick to match your existing 4gb stick is a good idea. On desktops it used to be better to have 2 sticks vs. 4 as sometimes having more sticks could cause instability. HOWEVER, not many laptops have 4 RAM slots and I haven't heard this same thing mentioned about laptops. I also haven't looked into this issue in a few years...

A number of folks here are running 16gb of RAM in W series machines, so hopefully they will chime in. Since you already have the 2x4gb set that you could use, plus the 1x4gb the machine came with, I'd likely just get another 4gb stick and not worry about any differences in performance which would be, unless I'm mistaken, highly marginal. Good luck!

[eecon]

Thanks wolfman ..... I've ordered thru Lenovo a matching 4GB module using the same FRU number and will simply do as you suggested ..... have the crucials in the first pair of slots and the Lenovo modules in the second pair of slots .... all matching specs. I already thru in the crucials and am running with 12GB tonight and will soon be running in dual channel mode when the other Lenovo module arrives.

Sure made a big difference going from 4GB to 12GB in everything!

[wolfman]

Nice, good deal. Yes, 16gb of RAM is nice to have (or necessary depending on workload). Enjoy the machine!