I first bought this from Amazon in Jun 2010 for ][. Now it is , so I thought this is a cheap way to upgrade to 8GB. On installing beside the original memory in the 3rd and 4th slots on my MB (MSI 790FX GD70), the PC would not boot up. I swapped them round and everything seemed to work OK, the pc recognizing the full 8GB etc. However, I have since been plagued by random BSOD and reboots which I can only attribute to this memory kit. The part numbers were also different from the kit from 7 months ago. I did do a memtest boot disk check, and it did 4 passes overnight without failing. However, the reboots still recur. I will do some more digging on the part numbers and timings, but beware - you get what you pay for.
OK, I've now taken the RAM out and it has "Version 3.1" on the sticker, whereas the same item bought in Jun 2010 had "Version 7". BIOS settings are the same with one exception - the TRFC is different. Although they are all 9-9-9-24, there is a difference in the TRFC timings. The Version 3.1 chips have this at 160ns (107) and the version 7 are 110ns (74). Corsair recommend that you don't mix versions. Separately, the RAM works OK - no BSOD for the past week with the newer 4GB set, whereas before it was almost daily with the mixed 8GB. However, together they are incompatible. If you are purchasing to upgrade an existing system, replace all the RAM together so that it matches.
Still Ok after 2 weeks with no BSOD or memtest or Prime95 errors. Good RAM but just won't play well with other versions.