dual channel ddr explained?

[Karlsbad]

Hi,

Can anyone explain what dual channel ddr is? Is it available now? Where? Is it on pricewatch? What designations does it go by? From reading posts in here it seems that it is going to be the best thing since whatever and boards supporting it will be out about the time I'm ready to build a system. I thought I saw a post referring to dual channel ddr333, this isn't the same old ddr333 is it?

 

[Crashman]

Same DDR333, used in parallel Pairs. Dual Channel simply takes two modules and mounts them parallel so that the memory bus is twice as wide. This way, you can get twice the data through in the same amount of time, while using (inexpensive) parts that already exist. Except for the motherboard. The first dual-channel DDR board for a P4 powered PC should be available in a few weeks.

Rambus is already dual-channel, which is why it works better for the P4 than single-channel DDR has.

nVidia makes a Dual Channel chipset for AMD, but AMD processors have such a slow bus in comparison that they can't actually get much use out of it.

It is possible to make a board that works both ways, but such a system would be much faster with two modules than with one, due to the increased memory bandwidth.

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[Skipper007]

Dual channel DDR is when a chip has not just one DDR bus, but two. For example, one DDR 333 module can move 2656MB/s. However, with two DDR modules and Dual channel DDR, the transfer rate is 5312MB/s. And yes, those are real transfer rates - most data in memory is processes more than once, so despite the fact you memory bandwidth will probably exceed the amount of memory you have, you will still get a boost in memory dependant applications.

Downsides of Dual channel DDR? You need two memory modules instead of one.

So far, only Nforce has Dual channel DDR, and current Athlons can't accept the amount of data generated by dual DDR all at once, but some of the upcoming Athlons will. Upcoming dual channel DDR chipsets include Nforce 2 (Athlon) SIS 655 (Pentium 4) and Granite Bay (Pentium 4). Oh, and one Xeon chipset with dual DDR has shipped, but it is more of a server design.

 

[Karlsbad]

This will probably seem ignorant, but what the hell, is it likely that SIS 655 will support prescott or 667 Mhz fsb? If so, then for someone not interested in overclocking it would still make sense to buy DDR333 because of the miniscule price difference between it and DDR266 compared to the performance boost one would get with a 667 Mhz cpu?

 

[jlanka]

Crash, I haven't been following the MB forum a lot lately, what is the chipset called for Dual channel DDR on P4, and who will be making boards with it initially?

<i>It's always the one thing you never suspected.</i>

 

[juin]

2 beer bottle trow as the same time vs 1 beer so double splash

Now what to do??

 

[Crashman]

It's called the SiS 655, and the first sneak peeks of such a board, the Asus P4SDX, have already made circulation. The chipset is behind schedule, supposedly because SiS needs the production space for a larger than expected volume of 648 chipsets. The rumored release time for the Asus board is about 2 weeks. Even if it flops like the P4S8X, other board manufacturers will probably release better versions soon after.

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[Dreadnaught]

so why the 333ddr instead of 400ddr? is it really true that the 400 boards run slower?
im calling today to cancel my 1066 rambus... bummer though, id have my computer running in 7 days.
i know this falls in another catagory but for this mobo, you think that corsair xms3500 is one of the best bets?
vs just buying their xms2700 and calling it a day? i always buy for overclocking but just build a new computer instead, though the cost isnt much more and it does run faster if pushed, but does it make a bit of difference to have the faster memory, overclocking reasons aside?

<P ID="edit"><FONT SIZE=-1><EM>Edited by Dreadnaught on 11/01/02 01:36 PM.</EM></FONT></P>

 

[Crashman]

Because DDR333 tends to be more reliable. Besides, the bandwidth of the P4 "533" bus CPU is 4.2GB/s. That means that in Dual Channel, PC2100 would be a perfect match. PC2700 would be a perfect match on systems overclocked to 166MHz bus clock, aka "667" bus.

There is a small advantage seen using faster memory than your bus can support, in that at the higher latency, each cycle is slightly faster in real time, so that Cas2 at 166MHz is less time than Cas2 at 133MHz. But we've already seen this on AMD systems showing a measly 1-3% gain.

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[Crashman]

It may or may not support Prescott. I haven't seen any info on this. The differences in chipset design to make former chipsets compatable with the newer processor are so small that if it isn't compatable with Prescott, they would probably release a slightly modified version that was.

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