Dual Channel ddr

[Brahma]

I'm not quite sure how this dual ddr thing works. let's say that I have an A7N8X mobo that supports dual ddr. to get the benefit of this, do i need to use 2 sticks of 256 meg ram rather than 1 stick of 512?

 

[Schryver]

Lemmesee... yes. For 2 channels, you need 2 sticks. One stick = one channel = big no-no on an nforce2 board. It would actually work (unlike RAMBUS), but your bandwith would be halved.

 

[Brahma]

Alright, makes sense. Thanks for clearing that up for me schryver.

 

[jankphil]

that's not acually true, you can run with 1 stick of ddr ram, but you won't get the extra push of the dual ddr without the 2 sticks.

"What kind of idiot are you?"
"I don't know, what kinds are there?"

 

[bum_jcrules]

FYI...

nForce boards have two memory controllers MC0 controlls DIMM0 and MC1 controls DIMM1 and DIMM2.

Q1 - Can it negotiate using three modules?
A1 - Yes.

Q2 - Can it negotiate one module?
A2 - Yes.

However, for the best bandwidth and optimal performance you should use two memory modules of equal size(Density), make/model , and clock frequency speed. Anything other than that will not be optimal.

<b><font color=red>Fredi</font color=red> <font color=red>Fredi</font color=red> He's our man! If he can't do it no one can!</b>

 

[Esso]

Are all those settings handled automatically by the controllers (based on ram being detected in whichever slots?); or is it some funky bios setting that you would have to enable?

 

[Schryver]

that's not acually true, you can run with 1 stick of ddr ram, but you won't get the extra push of the dual ddr without the 2 sticks.

It would actually work (unlike RAMBUS), but your bandwith would be halved.

Methinks I said that.

 

[bum_jcrules]

The memory controllers will negotiate the best interface to the FSB/Northbridge regardless. It will then build a reference signal based on what will interface the best between the two channels and the memory each channel is running.

These are basic illustrations and are by no means good ones but I hope you get the concepts.

Say you have... (Signal speed example)

DDR333 in DIMM0

DDR333 in DIMM1
and
DDR266 in DIMM2

The best way for all three modules to interface is at a DDR266 signal. It would be better to take out the DDR266.

Say you have this... (Density example)

512MB DDR333 in DIMM0

256MB of DDR333 in DIMM1
and
256MB of DDR333 in DIMM2

The channel densities are the same but the memory modules are not equal. The two controllers will have to negotiate between themselves. There would most likely be added latencies are involved due to addressing issues, etc.

Just use two modules of the same make and model. This way the speeds, densities, and the PCB and module configurations are the same. This will be the optimal setup.

The BIOS will have some memory settings; like allow you to change the latency timings, etc., but that is not necessarily how the controllers will use the memory.



<b><font color=red>Fredi</font color=red> <font color=red>Fredi</font color=red> He's our man! If he can't do it no one can!</b>

 

[igo_hams]

Is this possible:
256 ddr400 in dimm0
256 ddr333 in dimm1

The mb is a asus a7v8x. The manual says that if u use ddr400, you can use only one slot. But do they mean only one slot 400Mhz or one slot in general when using ddr400?

Me not so smart.

 

[bum_jcrules]

Sure, but the controllers will negotiate a reference signal down to the lowest common denominator, DDR333. If you only use the DDR400 in DIMM0 it will run at DDR400. Once you introduce a second module in either DIMM1 or DIMM2 or both it will negotiate down. If you don't mind both at a DDR333 signal, go for it. The bandwidth will be still be nice at DDR333. (Don't get greedy. )

Like I said above...

"Just use two modules of the same make and model. This way the speeds, densities, and the PCB and module configurations are the same. This will be the optimal setup."

<b><font color=red>Fredi</font color=red> <font color=red>Fredi</font color=red> He's our man! If he can't do it no one can!</b>

 

[karetsos]

I have a zenith 7njs nForce2 mobo.
i use 2x256 MB PC2100 CL2.5 Kingston ram modules,
and when i boot up, i get the message
Dual Channel DDR enabled, but only when i set the bios
settings at agressive.
I i try to change the bios settings, the message dissappears.