Thinkpads Forum

I read elsewhere that x220 could support 2*8GB 2133MHz memory with bios 1.28 and earlier. So does it support Kingston HyperX Impact http://www.kingston.com/en/hyperx/memory/impact - http://www.kingston.com/datasheets/HX32 ... 2K2_16.pdf ? Or would 1866MHz version be safer bet from Impact series as it has also 1333MHz jedec timings for fall back in case higher speeds don't work? Once I buy the memory sticks, i won't be able to return them.

Also I see 1866MHz modules have lower CAS values than 2133MHz modules. Which would be faster for graphics performance?

How much higher frequencies might shorten battery times?

So overall, which model to buy if any?

Welcome to the forum!
The following is a non-answer answer ... but it is the correct answer in this case:
Buy memory that has the same specifications as the memory already running in the machine.

Other variations may or may not work reliably, depending on chip and/or board manufacturer, and the only way to know for certain is to test and see the results. Even if other memory "flavors" work, the differences would be imperceptible, both in performance and battery life.