Dual Channel Memory?

[pahn]

I am building a P4 800FSB system, and am buying a dual channel DDR400 compatabile motherboard. Do I have to buy specail dual channel memory to take advantage of this? Or do I buy the normal RAM and it automatically works? All the memory I have looked at on newegg is 3.2 GB, and if I am not mistaken, dual channel means 6.4 GB?

 

[mechBgon]

Normal memory works fine as long as the modules have the same logical arrangement (meaning, you cannot mix two modules with different numbers of banks or chips on them and expect to get dual-channel working). If you buy the dual-channel kits, you're guaranteed to get two identical modules.

 

[pahn]

Originally posted by: mechBgon
Normal memory works fine as long as the modules have the same logical arrangement (meaning, you cannot mix two modules with different numbers of banks or chips on them and expect to get dual-channel working). If you buy the dual-channel kits, you're guaranteed to get two identical modules.

So your saying "normal" memory works fine. If I bought regular (3.2GB spec) DDR PC3200 RAM, it would work as dual channel on a dual channel mobo? I am planning to buy only one 512 mb stick. So your saying in the future, should I upgrade, I have to buy the same type of ram to keep dual channel running?

The thing I don't get is that u later say dual-channel kits... what is that? The motherboard I plan to buy says it supports both single and dual channel memory. If I bought regular (3.2GB) spec ram, would it work as dual channel or single channel on a mobo that supports both?

I guess my question is, is there special "dual channel" memory that is in existance?

Thanks.

 

[mechBgon]

All the memory modules in the dual-channel kits are "normal" 64-bit DDR SDRAM (well, unless they're R-ECC, in which case they're 72-bit ).

Look at the various Crucial PC2100 modules and let's take the 256MB PC2100 module as an example. They make three versions. One has four chips on it, another has 8 chips on it, and the third has 16 chips on it. You could get your motherboard to run dual-channel mode using two of the 4-chip ones, or two of the 8-chip ones, or two of the 16-chip ones. However, you could not do it with a mixture of them, because now the logical organizations of the modules don't match and so the motherboard cannot make a 128-bit wide "super-module" out of them anymore.

So the risk you run is that you'll buy a module, and then go to buy a second one and it is not the same. For this reason, you would want to buy a dual-channel kit so the modules are guaranteed identical.

 

[pahn]

Oh... I see. You have to have 2 modules to be dual-channel. Don't I feel stupid.

But it would work if I bought two of the same module (model) made by the same manufacturer right?

 

[mechBgon]

Originally posted by: pahn
Oh... I see. You have to have 2 modules to be dual-channel. Don't I feel stupid.

But it would work if I bought two of the same module (model) made by the same manufacturer right?

Well, yes and no. If they are in fact identical, then yeah. But look at those three versions of Crucial PC2100 I mentioned, and you realize something:

:Q ~ uh oh, they sometimes change the design of a given module as time goes by!

So let's say you buy a certain module today, and then the design gets changed from a 16-chip double-bank module to an 8-chip single-bank module. Problem. But remember... you can try it, and if it won't fly, then sell your single module off to someone and get a dual-channel kit at that time.

Bigger picture: you might consider getting one dual-channel kit consisting of two 256MB modules right now, and you'd still have a pair of slots free to add another two 256's or 512's later. How's that sound? This way your system will be performing at its peak right away, too (dual-channel really helps the Pentium4 hit its stride).

 

[butch84]

i agree with mechBgon on this one. I took the route of buying 2 x 256 sticks at a time, because i wanted dual channel, but couldnt afford more than 512mb of ram at the time. Now im running strong with 4 256 sticks to total 1gb of ram. Its not likely you will need to worry about having all your ram slots filled, since by the time you actually need more than a gig of ram, your setup will be slow anyway. unlesss you already do a lot of video editing or something.

anyway, thats my dos centivos.

peace