could somebody please explain what dual channel memory is and what motherboards are dual channel?

[hclarkjr]

i just got into the DDR memory scene and am a little behind the times, just need a refresher on what the differnet terms are and such. i have a abit at7 motherboard, is that a dual channel motherboard? thank you to anybody that replies.

 

[EeyoreX]

The AT7, while a nice motherboard (I have one too) is not dual-channel. On the AMD side of things, basically all nForce2 (and nForce1?) boards are dual-channel. However, dual-channel benefits are minimal, at best, offering, in best-case situations, a maximum of a 4% increase. Generally, less though.

\Dan

 

[LightForce]

There is no such thing as dual-channel DDR memory. There are only dual-channel memory controllers, which are part of a motherboard's chipset.

Some manufacturers sell sets of two memory sticks and advertise it as dual channel, but these are just regular DDR memory sticks packaged together to ensure that you meet the requirements of dual-channel memory controllers (memory sticks must be installed in pairs and must be identical). There's nothing special about these memory sticks.

~~LF

 

[mechBgon]

Currently, Intel has a couple popular DC chipsets for the Pentium4/Celeron, the i865PE and i875P. They use modules the way a RAID controller uses drives in RAID0, by reading & writing across two modules at the same time. There's also a version with integrated video, i865G. You can find both chipsets out there with either the ICH5 or ICH5R southbridges (ICH5R has native SATA support, including RAID capabilities). Given one or three modules, or modules that aren't logically the same (eg one double-sided, one single-sided), they'll revert to single-channel operation out of necessity.

AMD's side, for the AthlonXP there is nForce2 Ultra400 and its predecessor nForce2 SPP ("system platform processor"), and also the nForce2 IGP (instant gratification processor... or was it integrated graphics processor? hmm...). These have two memory controllers that access the modules in staggered fashion 1-2-1-2, not RAID0 fashion, and can deal with non-symmetrical memory arrangements without giving up dual-channel operation. nForce2 also comes in a non-DC version, the nForce2 400 (non-Ultra).

For the Athlon 64, the memory controller is on the CPU. The current Socket 754 models have a single-channel memory controller that can handle one or two modules at PC3200 speeds, and kicks down to PC1600 speeds if you add a third one, which makes your face look like this --> The expensive Socket 940 Athlon 64FX, and its server stablemates the Opterons, all have dual memory controllers and use Registered modules, but they will be joined by Socket 939 Athlon 64s with dual memory controllers this Spring.

The S939's will not require Registered modules and presumably will handle up to four PC3200 modules (two per controller), which is more like it, so a lot of people are looking forward to seeing Socket939 stuff like nForce3 250 variants, and VIA K8T880 or whatever they'll rename it to. But it's the CPU that has the memory controllers, so the platform's role is somewhat different with A64.

So DC DDR is where it's going to be at for this year. HTH