Why does more than 1GB of DDR cause massive slowdown?

[AFurryReptile]

I've had two seperate computers now, one Athlon 64 3700+ and the other a 4200+ X2, both 939 and running on 1GB of DDR. Adding more RAM to either of these just causes it to slowdown... up to a 20-25 fps decrease in something simple like World of Warcraft. What is the problem?

 

[ryderOCZ]

System specs on the PC's in question - What board? What ram? How many sticks in total (before and after upgrade)?

Did you check speeds and timings before and after?

 

[AFurryReptile]

It's hard to tell what board is on one - it' a stock HP board with 2x512 Infineon RAM. The other is an ASUS A8V-XE with no overclocking options, and 2x512 Corsair Valueselect. Because of the boards these are on, I don't have a way to check the timings. Both are running dual channel.

 

[myocardia]

Never run more than two sticks of RAM with any AMD processors. 2T command rate seems to kill their performance, and 2T is mandatory, with more than 2 sticks of RAM.

 

[AFurryReptile]

ah ok... thanks a lot!

Does this apply to AMD's AM2 platform too?

 

[myocardia]

Originally posted by: AFurryReptile
Does this apply to AMD's AM2 platform too?

It applies to all AMD processors made since the Athlon XP.

Command Rate is not normally a factor in Intel 478 tests, but it is a major concern in Athlon 64 performance. A Command Rate of 1T is considerably faster on Athlon 64 than a 2T Command Rate.

Here's a link to the article from which that quote originated.

 

[jmmtn4aj]

Originally posted by: myocardia
Never run more than two sticks of RAM with any AMD processors. 2T command rate seems to kill their performance, and 2T is mandatory, with more than 2 sticks of RAM.

But 20-25 fps? Isn't that a bit much?

 

[cmdrdredd]

Originally posted by: jmmtn4aj

Originally posted by: myocardia
Never run more than two sticks of RAM with any AMD processors. 2T command rate seems to kill their performance, and 2T is mandatory, with more than 2 sticks of RAM.

But 20-25 fps? Isn't that a bit much?

Since the AMD CPU is reliant on timings over speed I'd say yes it is possible. 1T on AMD systems makes a massave difference. On an Intel C2D running 1T does basically nothing at all. I can turn on 1T and get no fps gain. Sometimes even lose a bit (within the margin of error from run to run).

 

[mugen223]

so it is ok if i put 2 * 1 gb? or you are saying anything above 1gb is bad for amd x2 processors when using ddr ram?

 

[brawleyman]

I think that what he is trying to say is that it really doesn't matter how much ram you have, whether it is 512mb, 1Gb, or 2Gb, or more, what matters is that you have an even number of sticks, not 3 or even 4. When you have 3 sticks of memory, dual channel won't work (however I have heard of some motherboards still running dual with an odd number of sticks) and when you have 4 sticks, the motherboard is trying to utilize ram in 4 different spots rather than just 2 so the timing must be different, and therefore that is something that AMD cannot cope with very well.

 

[Bacstar]

This doesn't apply to AM2 anymore, does it? Isn't DDR2 automatically running at 2T timings now?

 

[brawleyman]

From what I understand, DDR2 can run at 1t and 2t timings...and with AMD, when you get to the 2t timing, it really slows it down, unless you have Intel, then it doesn't really matter. I think that a lot of that has to do with the fact that AMD has the memory controller on the die itself, so when timings have to change outside of what the memory controller can handle, it conflicts and hurts your performance rather than help it.