Originally posted by: CrucialLabs
Hello,
There really isn't any memory out there that is dual channel memory, it is a function of the motherboard. To achieve dual channel you need 2 modules that are the same MBs, speed, characteristics. If you were to buy 2 modules at the same time you would get memory you can use in dual channel. The slot configuration is this; the module have to be place in slot 1 and 3 and it is that simple. If you have 3 slots then filling all three slots would nul the dual channel function. Correct me if I am wrong on this, someone. Companies out there are selling memory in pairs and saying they are dual channel memory, not true.
Hope this helps.
With Intel dual-channel chipsets, the two paired memory modules are addressed as one virtual supermodule, 128 bits or 144 bits wide depending on whether it's non-parity or ECC. Hence the addressing scheme has to "fit" both modules, and thus they should be at least logically identical, if not physically identical. So a single-sided 256MB DIMM plus a double-sided 256MB DIMM is gonna cause Problems
😛 For the Intel DCDDR setups, you can have a second pair of modules and they have to match eachother, but they don't have to match the first pair.
The nForce2 chipset has two memory controllers, but from what I've read on the subject, they can both access all of the memory modules via a crossbar (shades of a GeForce-class GPU? go figure
😀). For a comparison, the best analogy I'm coming up with is your OS's page file... Intel's solution is something like having your pagefile on a two-drive RAID0, while nForce2's solution is like having two pagefiles on two independent hard drives. You'll notice that nVidia calls their nForce2 setup "Dual DDR," not "Dual-Channel DDR." A slight distinction.
🙂
As a result of the crossbar setup, nForce2 doesn't lose dual-channel mode when using three memory modules. Going back to what the OP was driving at, the additional bandwidth of DCDDR helps Pentium4 systems perform well, but is not really a huge boost to an AthlonXP in most situations... for AthlonXP, the glass is already 95% full with just one DDR channel, if the CPU is the only thing needing the bandwidth.
An AthlonXP system that's using an nForce2 chipset with integrated GeForce4MX is where the bandwidth of Dual DDR begins to show some results... the 3D gaming performance typically goes up quite a lot, like 40%+, based on AnandTech's benchmark results.
