Hello. I was curious as to how dual channel ddr works. My board has dual ddr400 and I'm currently running 2 sticks of 256 and 1 512 (mobo has 3 slots total) for a total of 1 gig of pc3200 memory. I want to take advantage of the dual channel capability and was wondering what would be the best configuration for it. The two 256's are matched corsair sticks, my question is if i'm just using these sticks are they automatically going to be put in dual channel mode or how exactly does that work?

Thanks

I just picked up 512mb (2-256chips)of Dual channel memory before I had pc2100 running at 400(or pc 3200) I heard that u could run in dual channel mode and also run another chip in the open bank. so I played around with it there right I have 1 gig of ram and it says its running dual channel. I have not bench marked it yet but did play nascar 2004 and it was faster with the gig rather then 512 dual channel.
I run a K7N2 mb, 2500+ overclocked to 3200+
One strange thing is before to get my ram to run at 400 I had to go way down on the timmings 12-6-6-3
Now it can run at lowwer timming 6-3-3-3
I will let u know more when I get done with my tests......

dual channel is enabled only if your memory is in Bank 1,3 or 2,3, or 1,2,3.

As furball says, HAS to be in memory banks 1 and 3, 2 and 3, or all three, to run in Dual Channel mode.

ok, i now have the twin pair in slots 2 and 3 just for testing purposes...is there a way i can benchmark or test it to see if its running that 128 bit dual channel mode rate?

This has been discussed many times before...there is little or no advantage to running dual channel on the socket A platform. The way the architecture is designed, your memory bandwidth cannot exceed your CPU bandwidth...so if you're running a 3200+ CPU, your memory bandwidth cannot exceed 3200mb/s. There's nothing you can do about it. Running PC3200 in dual channel mode gives the potential of 6400mb/s (3200 x 2), but you're still limited by the CPU's bandwidth of 3200mb/s, so there's really no point of running dual channel. Single channel PC3200 is the way to go with the socket A.

Theoretically, you could run PC1600 in dual channel mode & attain 3200mb/s & save yourself some bucks, unfortunately PC1600 won't run at 400DDR FSB.

Got into this discussion a while ago in the gaming forum...check this post & the included links, it should explain more clearly

http://www.computing.net/gaming/wwwboard/forum/862.html

In DC channel mode one chip gets info ready for the next action and so each chip is really doing half the work would that not make for better performace??????

Yes, if you use Intel P4 800 mhz processor. As Jam has explained it is not with Socket A XP processor. You could also go with A64 that would do it also.

No all I'm saying is there should be a benafit even with socket A if the memory only has to do half the work.

But when I did open the dc memory it did talk about the intel fsb of 800 and 533 i think.

Also I have not benchmarked the memory yet but it does run faster in dc mode then in single channel mode. It does run faster with all three slots making 1 gig rather then 512 of single or dual channel.

Take it from a degreed engineer with a computer business on the side, Jam knows what he/she is talking about when it comes to dual channel memory. It has been widely documented that it provides no performance increases in the Athlon XP. Remember, there is a difference between running in true dual channel mode and having chips in multiple RAM slots.

Some thoughts for FBI Agent:

CPUS
- In my business I normally direct my customers toward the Athlon XP with the Barton core. This chip simply provides more bang for the buck when compared to the Pentium 4. Just make sure you get a processor with at least a Barton core. These start at the XP 2500+ and go up. The Barton core is a definite performance jump from the earlier Thoroughbred processors and will run at a faster FSB speed. Also, the RETAIL version (not the OEM version) of processors usually come with a fan which is sufficient for keeping the processor cool.

MEMORY
- Your choice of 512Mb is sufficient and should run any program well. For games I would recommend PC3200 with a CL of 2.0. Just make sure you stick with a brand name such as OCZ, Corsair, or Kingston and you will be OK.

HARD DRIVE
- I would make sure that your hard drive has an 8MB cache (not 2MB) and is a 7200RPM model. The hard drive has become one of the most critical bottlenecks in systems today, so buy a good one. A RAID 0 system may also be a good choice due to the nearly 100% increase in hard drive speed. This feature requires at least two hard drives to operate. Many manufactureres include a RAID controller on their higher end motherboards, so a controller card is not required. Usually I point my customers in the direction of Maxtor drives simply because they transfer data slightly faster at 133Mb/s versus the standard 100Mb/s.