I have 4GB of spare Corsair XMS2 DDR2 CM2X2048-6400C5 sitting around. It is a set of two DIMMs.

I currently have the exact same set in my PC (accept for the version number on the stickers, one set is V3.2, the other V3.4). I am thinking of adding the extra two DIMM/4GB of RAM into my PC, but I am wondering if it will be stable? I've read in that past that some motherboards have stability issues with more than two DIMMs, so I would like to know if this is something to be concerned about. I do not OC and have no plans to, so that is not an issue. In the end, I will have 8GB in 4 DIMMs.

Assuming it is stable and works fine, will my RAM still be working in duel channel?

Relevant system specs:
ASUS M3N78 Pro with latest BIOS
AMD 965
Win 7 Pro 64bit
GTX 260
Antec 500 Earthwatts

Under your conditions (no OC), it will probably work. Nearly every MB and CPU are designed for it. Its funny that it does not always work perfectly.

Strictly speaking, the memory probably will "slow down" imperceptibly (go from 1T timing to 2T timing) -- this will not affect FPS and is offset by having more memory for programs that use it. In one case, my memory stayed 1T -- this is an automatic setting by the BIOS -- you need do nothing.

On the other hand, if for no apparent reason every so often on a regular basis (maybe days apart) the computer freezes or does something equally "suspect" that it never did before -- it might be the extra two sticks (at least, that's what happened to me -- currently running 4 sticks of different memory in a different MB OK). Then remove 2 sticks and see if the problem goes away.

Based on my personal experience FWIW.

So will I see a decrease in performance for programs that use under 4GB of RAM when going to 8GB? I am reading it will slow down from 800MHZ to 667MHZ. Is this true, and will the motherboard do it automatically?

In addition, I am being told on another forum that I will manually have to do the following:



Would I really have to do this to make my RAM run stable? Is there any harm in increase the volts? Last thing I want to do is fry my motherboard/CPU.

If it works correctly, you should NOT see an FPS slowdown (you might measure a "microscopic" slow down -- a fraction of an FPS). If it was running at 800, it should still run at 800.

If it does go to 667, that will cause a very slight slowdown. But, much less than one might think -- only a percent or two normally -- because memory is not the bottleneck in most programs. You could manually reset in BIOS to 800 -- I don't know enough to say, in your case, that would work perfectly. If it didn't work, then use 667 or take out the extra sticks.

For example, my current memory is 4 sticks of 1866. It runs at 1600 with my Phenom II. But, the system wants to run it at 1333. So, I let it. In testing with 3DMark 11, there was essentially no difference in FPS, and a very small difference in the CPU score -- between 1600 and 1333.

When I originally changed from 800 speed memory to 1333 speed last year, I checked FPS in games and benchmarks. No change.

In general, AMD processors have been more sensitive to timing (e.g. CAS 7 vs CAS 8) than memory speed. Usually, faster memory has longer timings, so it all comes out in the wash -- no significant improvement with faster memory -- or slowdown with slower memory. In my experience.

I did mess with the NB. By increasing the NB speed, I got a small measurable improvement. But, it was unstable without increasing NB voltage. I did not think the minor improvement was worth any risk. So, I set things back to normal (used automatic settings in BIOS).

There are exceptions to every rule, your mileage may vary

Ok, I will try to insert these in. Hopefully they will work at 800.

Here is what my memory current looks like:



I'll post the results when I get the other RAM in.

Flogger, I have the exact same two sticks of Corsair memory running with two sticks of a completely different brand (OCZ Reaper (OCZ2RPR800C42G)) and I find the stablility pretty damn good since I overclock the hell out of my CPU and RAM



Corsair is good memory.

I installed them. Settings are the same, just 8GB now.

I played Crysis Wars for a bit with no issues. I will try the BF3 beta in a few minutes. But so far it seems to be working just fine.

I've had some crashing/programs stop responding as of late. I am wondering if these sounds like a RAM issue?

1) I was playing Crysis Warhead. The game randomly crashed to desktop. This actually happens every now and then, so I initially thought nothing of it.

2) ArmA 2 randomly stopped responding the other day. Odd because I never got that issue with that game.

3) Just now I exited ArmA 2 and the program stopped responding.

The BF3 beta runs fine though. Otherwise I have not been doing anything intensive as of late.

Do these crashes seem like they might be RAM compatibility issues?

That's the symptom I had in the past. When I went back to two sticks, the symptom went away. This happened with different memories in different motherboards -- but not with every memory and every motherboard.

Currently, I'm running 4 sticks at 1333 with no problems (different MB and DRAM than the ones that gave me a problem). Those 4 sticks gave me the same symptom at 1600 (overclocked) when running at normal DRAM, NB voltages.

So, for me, those little occasional hangs seem to indicate a DRAM related issue (though the real problem may not always be the DRAM sticks themselves). Don't have enough data points to be sure though.

Some mobos just can't power all four sticks evenly and that is where the crashes come from. Like Intel's old 965 chipset mobos, the distance from the memory slots to the northbridge was a critical factor in OC. In other words, some 965 boards would OC much better according to which slots the memory was installed in. My board has slots 0, 1, 2, and 3 in that order. My board will not boot without slots 1 and 3 populated.

Now, most good boards will run with all four slots full. Lower spec boards will produce problems. And different timings or voltage needs and brands will bring about problems too.

So the only way for me to get over 4GB of RAM stable is to upgrade to a new motherboard?

The RAM kits are identical.

I would bump up the voltage on the northbridge one notch and set the voltage for the memory at 1.9 manually.

Not necessarily...I would first loosen your timings. If that doesn't work then increase voltage like SpeedBunp said; and if neither of those work you could try lowering your FSB and drop the MHz on the RAM (if you have an unlocked multiplier for your CPU, you can increase it which would let you balance the CPU speed vs. FSB speed).

Don't go more than one notch higher on the memory voltage. Forgot to tell you that. I think they are rated at 1.8 so 1.9 won't hurt them. Memory will go up in a puff of smoke with aggressive voltages. I read the northbridge gets very hot on that mobo too and that could be the problem also, or part of the problem. Stick a fan over it someway. I'm assuming you are not using the integrated video chip.

What setting for the timings should I try? And I am assuming this is done in the BIOS? Where would I find the option to adjust the timings? I looked in the motherboard manual briefly and it doesn't seem to mention anything about how to set the timings.

unfortunately after reading more on your mobo, it doesn't look like your BIOS version has those options (unless they somehow added them in the latest updates). You may just have to skip timings and increase the voltage like Speedbump said

in Asus there is very great feature which allow you to share memory between graphics and CPU... so make sure you are dividing your memory according to requirements ....