Dual Channel DDR

[chris86]

Could someone explain what Dual Channel DDR is and how much faster is a computer with dual channel RAM to one with standard RAM?

 

[Greeno]

I'm guessing you know how RAM works, Dual Channel, is far better than Single channel mode mainly because it effectively doubles the memory bandwidth you have.

i.e.

Assuming you know :-

266MHz = PC2100 or 2.1GB/s Peak theoretical Bandwidth
333MHz = PC2700 or 2.7GB/s Peak theoretical Bandwidth
400MHz = PC3200 or 3.2GB/s Peak theoretical Bandwidth

Armed with that knowledge, because Dual channel effectively has 2 channels, it DOUBLES the read/write etc..

so, say you have 1x512MB PC3200 Dimm you can achieve 3.2GB/s, but if you have 2x512MB PC3200 in dual channel mode (requires a capable mobo) you can effectively get 6.4GB/s.

Hope that helps

 

[chris86]

Yup, it helped. Thanks!

 

[tripleione]

Dual channel will never reach anywhere near those theoretical speeds because of the FSB limitation.

 

[Krugger]

don't some of the newer computers have a 800 mhz fsb though?

 

[Greeno]

Exactly, Dual channel 400MHz is capable thru the 'c' brand P4's.

 

[NoisySilence]

Or with an Athlon64(-FX)/Opteron.

 

[Greeno]

very true

 

[Didou]

Allthough it's often mentionned as Dual Channel Ram, it's only the memory controller which has two channels. The Ram running in a dual channel config is no different then the one running in a single channel system.

It's still DDR-SDRam running in both, the only difference is the dual channel system has DIMM slots for each channel, whereas the single channel system's slots are all connected the single channel.

For example, in the following pic, the two upper slots are the channel 1, & the one at the bottom is the 2nd channel.

In the next one, the two upper slots are channel 1, & the bottom two are channel 2.