Mobo manual says to use "identical" memory in all slots. Why?

[SuperMarioBro]

So I have an ASRock Pro3-M Z68 motherboard with four memory slots. Right now I am using two of these:

http://www.newegg.com/Product/Produc...82E16820231311

And I am considering adding two of these in the two remaining slots:

http://www.newegg.com/Product/Produc...82E16820231426

However, the manual for the mobo, as the title says, tells me to make sure to use "identical" memory if I use all four slots. I don't really understand why. For one, I thought you only needed identical memory when the DIMMs were on the same... channel? Sorry, you'll have to excuse my poor knowledge of terminology here, but hopefully you know what I'm talking about. For another, I'm not really sure if these are technically NOT identical memory in the first place. They have the same size (4GB), same speed, same latency, even the same brand. But they are different models.

So in summary, will the memory I'm thinking of adding work for me?

 

[greenhawk]

that ram will work, just at the speed of the slowest.

As to ram size, it can cause issues with some situations, but that is more bentch mark areas as any ram is better than no ram.

 

[dave_the_nerd]

It should work fine. I suspect the motherboard manufacturer is just hedging their bets about memory compatibility.

My motherboard will run any two sticks of my RAM at DDR2-800 speeds, but populate all four slots and it won't run stable past 700 MHz.

:shrug:

 

[SuperMarioBro]

Yeah, I had a feeling they might just be trying to cover their butts. In terms of using all four slots, I think I've read that using more slots can make your system a bit more unstable as you overclock. Not sure how true that is, especially in my case since I have a 2500K with a pretty modest overclock (4GHz... although it already reaches like 69C at load).

Anyways, I guess I'll go ahead and buy this memory then. Looks like the "2N" latency and heatsink are the only difference so far as I can tell.

that ram will work, just at the speed of the slowest.

You just mean if I had two sticks of 1600 MHz and two of 1333 MHz, they would all operate at 1333 MHz, right?

 

[Meghan54]

Actually, there is absolutely no difference between the two sets outside the heatspreaders and one being called Ripjaws and one RipjawsX.

Both are rated 9-9-9-24-2N, according to each set's webpage on G. Skill's website.

http://www.gskill.com/products.php?index=233

http://www.gskill.com/products.php?index=345


Notice under speed rating, both are 9-9-9-24-2N. Just the Newegg page left off the 2N on the Ripjaws X set.