Dual channel memory question

[Cypher19]

Hi, first I'll give some background on my situation...

Recently, I bought a Corsair 2x1024MB pair of dual channel DDR2 PC6400 memory sticks (link) and when they came in, one of them didn't work (the system won't even POST if that specific stick is inserted). I don't have any fallback DDR2 memory, so I'm stuck with 1GB for the next four months until I'm away from my computer for awhile, giving me a period with which to RMA the suckers, since a) I'm not sure how long the RMA will take, and b) 1GB is better than 0GB

Anyways, I recently came across a deal for a different pair of memory sticks (2x1024MB, dual channel DDR PC5400) and I'm tempted to buy them, however, my purchase depends on the answer to the following question:

If I put in all four sticks at the same time correctly, i.e. I match up each stick with the right DIMM slot, will my system work properly, even though they're all dual channel? What about the fact that they're different speeds (or, what if they're the same speed?)?


Oh, and in case this changes the answer at all, here's my mobo and cpu:
Asus P5B-plus
Intel Q6600 (Kentsfield @2.4GHz)

 

[BillParrish]

If I put in all four sticks at the same time correctly, i.e. I match up each stick with the right DIMM slot, will my system work properly, even though they're all dual channel? What about the fact that they're different speeds (or, what if they're the same speed?)?

If I read you question correctly, you are asking what will happen if you install the 2 x PC6400 sticks and the 2 x PC5400 sticks.

The documents for the Intel P965 chipset are here:
http://www.intel.com/design/chipsets/P965/documentation.htm

and the one you want is this one:
Intel® P965 Express Chipset Family Datasheet: For the Intel® 82P965 Memory Controller Hub (MCH)

and in section:

10.2.1.1 Rules for Populating DIMM Slots

In all modes, the frequency of system memory will be the lowest frequency of all of the DIMMs in the system, as determined through the SPD registers on the DIMMs.

In Single Channel mode, any DIMM slot within the channel may be populated in any
order. Either channel may be used. To save power, do not populate the unused
channel.

In Dual Channel Asymmetric mode, any DIMM slot may be populated in any order.

In Dual Channel Interleaved mode, any DIMM slot may be populated in any order, but the total memory in each channel must be the same.

In Flex memory mode, any DIMM slot may be populated in any order per channel, but
each channel must have at least 1 DIMM. The matching amount of memory per
channel will be run in Dual channel interleaved mode and the remaining unmatched
memory will run in Asymmetric mode.
-------------------------------------------------------------------------

So you should not have any issues at all if the bios guy did his job correctly. You want dual channel Interleaved mode for the best performance. From above the sticks will run at PC5400 memory speed, at the loosest timings found in the SPD ( probally 5 5 5 15 or 5 5 5 18) and actually as long as the total memory in each bank is the same, the order you plug them in does not matter. (But I would still do it like you are planning)

You can of course over-ride the speed and timings in the bios with manual settings as long as they end up compatible with all sticks. If all sticks can run 4 4 4 12 at PC5400 speeds, it will work fine, If only one stick cannot for some reason do 4 4 4 12 then you will have to live with whatever the weakest stick can do for both speed and timings. If that PC5400 will OC to PC6400 speed at 5 5 5 15 timings you could run a 400MHz FSB at 1:1. So default settings are no problem, manual settings will require some testing to determine the maxium you can get out of the mix.