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AMD Phenom II x4 840 RAM/Memory advise, please.

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New Member
May 11, 2016
Could someone please give me a bit of advise on ram (speed) and compatibility with my CPU, please?

I hope this makes some kind of sense...

I have a AMD Phenom II x4 840 and 8Gb ram (2x4Gb stick 1 is Hynix 128000U 1600MHz, and stick 2 is Elixir 128000 (I think) 1600MHZ.

My question is........is my ram too fast for my cpu or would the cpu downgrade the speed to what it can handle.

The reason I ask is because my system has become unstable in the past couple of weeks or so. And in the research I've done I've found that my cpu can use a max ram speed of 1333MHz.



"That Backfired" Senior Member
Jun 5, 2013
Go Blue!
:welcome: to the forum Sconly!

The max SUPPORTED speed is 1333Mhz (source), however that doesn't necessarily mean you can't run faster. The only way to truly find out what that particular CPU maxes out at is to try it. I would guess you could run at 1600Mhz but there are no guarantees to this.

IMO your instability is likely caused by running mismatched ram. Mismatched ram can cause instability even if all the timings are the same. To find out for sure pull one of the sticks out and see what you can get it to. Swap sticks and check again. The CPU wont alter the speed/timings but your MB BIOS might.


Senior Member
Dec 27, 2008
I would get it stable with the RAM at 1333 mhz first and then see if you can push the envelope. It might mean relaxing timings and/or increasing RAM voltage a bit. And even if you can't get full 1600 mhz out of the RAM you might get say 1500 mhz. In my experience with those chips I could usually get the RAM to run 1500 mhz without a lot of fiddling.