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4GB Memory

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I am kind of in the process of spec'ing out a next-gen system. I'll definately have an Athlon 64 dual-core, and will be running at least Win Vista Ultimate 64bit. The 64bit OS would make larger memory configurations a reality, so I was thinking since this system (which wouldn't even be built for another year at least) would be intended as both a high-end gaming platform as well as my main system for a number of years, it would be wise to put 4GB of system memory into it. (If I were to build the system right now, 2GB would be the minimum, but I would still be considering 4GB). Of course, the only memory I'm considering is Corsair's. My questions arise from the fact that I simply don't have the experience with this much system memory, as so far I haven't run an OS that's been able to utilize that much.


My first question is, if I were to get two [identical] sets of TwinX (four modules) would the system still be able to operate in dual-channel mode, or is dual channel purely for exactly two modules?


Now even though I want a performance-oriented system, I do not plan to overclock initially, but I want good memory both for that future performance as well as for current headroom. Specifically, I want to be able to run the memory with respectable timings at normal speeds (i.e., DDR400 or DDR2-800, whatever the system is ultimately based on). I realize that the extra modules may restrict timings, but even with 4GB what do you suppose I'd be able to reach if I used the higher-end modules at stock speeds? For example, the TWINX2048-3200C2 is rated for 2-3-3-6 at I believe 2T, while the TWINX2048-3500LL is 2-3-2-6-1T. If I ran each of those sets at 400MHz, only with double the modules (for a total of 4GB, to be clear), I would expect worse timings from the TWINX2048-3200C2 than it's stock 2-3-3-6-2T simply from the presence of the extra modules, but what about the TWINX2048-3500LL? When run at 438MHz the set provides great timings, but what could I expect if I ran two of the pairs at only 400MHz?


Similarly, if I was using DDR2 in a system, the TWIN2X2048-6400 operates at 800MHz with 5-5-5-12-T1 timings. I'll assume a Socket AM2 system using DDR2-800, so this set operates at that frequency at those timings already; doubling the order for 4GB would necessitate slightly slower timings, but what would anyone suppose they'd be? I know this is a difficult question because this hardware isn't available yet for AMD systems (I think the new socket will be launched in the next few weeks, though!), but any speculation would of course be appreciated.


Thanks in advance!




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4GB is no problem.


With current systems people are running that much RAM. As long as you have 64bit WinXP there is no problem.


4 sticks of RAM will be 2T almost always.


Overclocking will depend on the RAM involved and as such is IMPOSSIBLE to predict. If you search around the net you will find people that are running 4x1GB RAM sticks and you can read about what they have done with them.


Dual channel works with EVEN numbers of RAM sticks.


Basically if you want maximum speed use one stick of RAM. Each stick you add will reduce the max overclock you can get. 2 sticks of RAM will get you good overclocks but 4 sticks WILL be less than 2 sticks.


If you are going to wait around for AM2 then wait around for 2GB DDR2 modules and run 2x2GB. That way you can upgrade to 8GB later and in the meantime run 2 sticks with 1T timings.

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Thanks for the reply, AusTerro!


I know that some users with 64bit OSs have 4GB of system memory or more, but I'm saying I'm not going to build a system with that much memory, and with a 64bit version of Windows, until there is better support for both hardware and software. Hopefully, by the time Vista is released this will be true.


I kind of figured what you confirmed about dual-channel was true; I just wasn't sure if it was a motherboard-dependent implementation (i.e., some boards only support DC with two sticks, and revert to single-channel with any more, even 4).


Now I'm not really concerned with overclocking at the moment (when I build a system, I just want to get it up and running and stable, and later on when it's getting old and slow I worry about overclocking). I'm mainly concerned about getting good timings at standard speeds.


I really think you've offered me with the best advice here, though: use 2GB modules (when available). Since I'll be waiting a while both for other components to be available (Socket AM2 and motherboards, GeForce 8-series, etc.) I might as well wait for fast 2GB modules from Corsair (which will probably be around by the time I'm actually ready to build the system).


So I guess, then, that my original question was asking how well an existing memory solution (two pairs of identical modules) would work. The answer is to simply wait for a more appropriate combination (a matched pair of 2GB modules).


I'm still kind of wondering, however, what kind of performance increase one could achieve when using a higher-rated module (or pair) at lower speeds; just for example, the TWIN2X2048-6400C3 has 3-4-3-9 timings at 800MHz, while the TWIN2X2048-8500C5 has 5-5-5-15 timings at 1066MHz. If the TWIN2X2048-8500C5 was run at 800MHz (in essence, underclocked), what might the timings be? Could they be slightly better, since the set is higher-performing and wouldn't be stressed as hard is it could go, or could the timings be equal or worse to the first set, since the latter was merely selected for being able to run at the higher frequency and isn't necessarily amazing at a lower frequency? Just wondering. I'm thinking maybe the lower-speed memory is higher-quality, and the faster stuff is just on the market because it's stable at those speeds.


It does look like I'd really have to wait for just a single pair of appropriate modules if I want the best command rate. I'm a little confused, however; most of the time, at least as far as Corsair is concerned, they don't specify a command rate, however occasionally they will, if it's 1T. Does this mean that for the most part, these DDR and DDR2 modules (and pairs) are only stable at 2T? Or are they 1T but the descriptions are simply lacking that information? And what about 0T? Is that a reality for at least any current DDR or DDR2 memory?


Thanks again, I really appreciate your input!

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I'm not sure about the 1T vs 2T stuff. I have a Gigabyte MB for my HTPC and it does NOT like 1T.


After doing some more research it appears alot of gigabyte MBs have trouble with 1T.


As for faster rated sticks and underclocking them for faster timing. Well sometimes it works and sometimes it does not.


It is always a good idea to get the RAM that runs at stock what you want. that way you know for sure what you are getting.


Some RAM ICs only like particular timings no matter what speed you are running. BH-5 for example only works with 2-2-2-X timings, but TCCD can start at 2-2-2-5 at DDR400 and then scale upto 3-4-4-8 at DDR600, where the BH-5 always needs to run 2-2-2-X and is only good for DDR400 to DDR500ish.


DDR2 will be changing alot in the next couple of months. Once the demand goes up (from AM2), we should see a bunch of new stuff released. It is hard to say what DDR2 will perform like on AM2. There is not much data out there yet. So I would wait a bit until other people tell us their results.


However I am very happy with my s939 setup. I was running 4x512MB sticks of Corsair BH-5 at 2-2-2-6 DDR500 T2. I took a pair out to put in another machine. But still worked without flaw and was super fast. So my s939 system does everything I want it to do. As does my older s754 system.


If you can wait for good 2GB sticks to become available. If not, there is some excellent s939 stuff out there.

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Hmm, I've had good experiences with ASUS mobos, so I was thinking about getting one of theirs once they have some good AM2 solutions. I've never had a Gigabyte board before, though.


Anyways, I think you've given me good advice yet again, regarding using RAM whose performance characteristics are known for certain.


Additionally, I never really thought about the current state of DDR2; my current systems use no better than DDR, as have the Athlon systems that are currently available to us. You're right about how now that AMD chips can use DDR2 there will be a ton of new offerings. Incidentally, I just started reading some reviews of AM2 setups.


I'm definately going to wait for 2GB DDR2 modules, however. You've helped me greatly. Thanks again!


If you're interested, I can post the preliminary specs for the system I'm contemplating. It'll be at least a year, however, before the system is built, since I have to wait for some new parts (like the memory, AM2 mobo, etc.) as well as the cash, so the final result will probably be at least a little different.

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