Hi!

Officially, 8GB is the maximum amount of memory that the X220 is supported for, i.e., tested and verified to work with. That said, I have 16GB (2×8GB DDR3 SO-DIMMs) installed in mine and it seems to work fine without any problems. Lenovo ThinkPad X220 Tablet - 12.5' - Core i5 2520M - 4 GB RAM - 320 GB HDD - with UltraBase Series 3 429842f Lenovo ThinkPad X220 Intel Core i5-2520M (2.5GHz, 3MB L3, 1333MHz FSB) 42873ku. Lenovo ThinkPad X220 is a Windows 7 laptop with a 12.50-inch display that has a resolution of 1366x768 pixels. It is powered by a Core i7 processor and it comes with 4GB of RAM. The maximum amount of installable memory is 16 GB in two memory slots, allowing for dual-channel RAM. Just like the X220, it is possible to use a mSATA SSD within the second Mini PCI Express slot instead of a WWAN card. Full review - me on Twitter: https://twitter.com/#!/and.

I'm curious about the real benefits from using 1600/1866 MHz RAM. Are there any? I assume no.
Intel's datasheet for i7-2620M says that this CPU supports only DDR3 1066/1333

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(Check Memory Specifications here: http://ark.intel.com/products/52231/Int ... apkw=2620m)
So, what's the real deal with it?
p.s.
I got 16GB of 1333 MHz RAM and i7-2620M and it works great. However I never tried 1600 or 1866 RAM.
Also I've been able to find modified BIOS 1.40 with memory support range unlocked. And I'm wondering why Lenovo
has limited this range to 1066/1333 in the newest BIOS versions while old versions (as people say) had supported
1066/1333/1600/1866 MHz RAM). So why Lenovo has enabled all four frequencies in the first place? And why Intel says

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Lenovo Thinkpad X220 Ram Slots

that only two modes are supported? Some strange stuff here.

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Thanks!