Dual Channel - 3 DIMMS - Might this work?

[gimpycow]

Hello everyone,

I currently have the following memory (2 256MB Sticks) running in dual channel on my ASUS NForce 2 motherboard:

Corsair Extreme XMS
XMS2700 333MHz CL2
CMX256A-2700C2
XMS 2702v2.1 0251043

My bios has the following memory settings:

SDRAM Active PreCharge Delay - 7
SDRAM RAS to CAS Delay - 3
SDRAM RAS PreCharge Delay - 3
SDRAM CAS Latency - 2T

I would like to match this memory with a 512MB stick to have a total of 1GB running in dual channel. To do this, I would need to put the two 256MB sticks in slots 1 and 2 (channel 1) and the 512MB stick in slot 2 (channel 2). However, I have read where pairing sticks of memory can be tricky for dual channel.

I was wondering if the following 512 MB stick might do the trick and be compatible?

Corsair CMX512-2700C2 512MB DDR333 PC2700 XMS Memory w/Heat Spreader Retail
512MB PC2700 (DDR333) CAS2 SDRAM w/ heat spreader
Tested at CAS latency of two cycles, command rate of 2T


I found the above stick for $109. Do you think this would work with the two 256 sticks I already have in dual channel? I would rather not have to purchase two 512MB sticks if I don't have to. I know I had posted before and was warned against doing this but these sticks seem to match up fairly closely. What do y'all think?

Finally, the bios settings that I have above are set to "optimal" for stability. Should I look to tweak those settings in the bios?

Thanks in advance for your help!

 

[ohGrFreak]

I seriously doubt it will work, i'm almost positive it won't. I am almost sure that when running dual channel you need matching sticks (2x256 or 2x512 or 2x whatever) not three sticks and only two match, and those are on the same channel for pete's sake, LOL. Your theroy made me thing twice though, because technically on channel "a" you have 512 and on channel "b" you will have 512. It's a very interesting proposal. What does your Motherboard's manual say about it?

 

[ShoobieRat]

You have to have a matched-pair of memory sticks that support dual-channel. They have to be the same, and in the dual-channel slots of the mobo. If you have 3 sticks of memory, dual-channel is pointless, since the third chip is going to be like a 5th wheel to the process. Also, if you have two 256mb chips in dual channel, and then a third stick of 512mb, the 512mb stick is going to bog things down as it'll have a slower latency and thus bring everything down. Of course, you could spend just shy of a Grand and get ultra fast memory for that 512, but it would still defeat the purpose of dual-channel.

You're better bet, if your mobo can support it, is to ditch the 256mb chips and just buy two fast 512mb chips and run them in dual-channel. Slightly expensive, but much much better.

If your 256mb sticks are fast, and your 512 is fast, don't worry about dual-channel. You'll likely not see a difference anyway.

 

[Blueman]

Why ditch the 256 meg sticks Shoobierat? if they buy another 512 stick, and the MTB has 4 slots, then put a 512 and a 256 in each channel, then you, in theory, would have 1.5 gig of ram in dual channel mode. Of course there's always the compatablility issue, and whether the mtb will support such a configuration.

 

[ShoobieRat]

Yer dual-channelled 512's are going to be slower than your dc-256's. Besides, at 1.5gb of RAM, the dc difference isn't going to be very noticeable. It's always best to keep things consistant.

 

[Nubius]

Actually he's right in thinking that he can obtain dual channel.

Although it's not at all common and personally I really doubt you'd get it to work, but yes you can with some luck and a prayer, obtain dual channel by placing 2x256 in slots 1 & 2 and then a matching 512mb in slot 3.

Like I said this is pretty rare that someone can actually get it to work and the sticks would have to be EXACT for any hopes of it working, so you'd probably have better chances of it working if you say bought all 3 sticks at the same time instead of buying one down the road.

Even when you are just trying to get dual channel with two matching sticks bought at seperate times sometimes computers can be fickle and decide to still not work in dual channel.

From what I've gathered DC can be tricky and iffy sometimes unless you get specifically a DC brand ram which all that means is those two sticks have already been tested and are guaranteed to run in DC.

Overall though, yes it is possible.....will it work for you?....well that's somewhat of a gamble. Only one way to find out though

 

[gimpycow]

3 DIMMS of different sizes can work.

2 256 sticks in slots 1 & 2 = 512MB in channel 1.
1 512 stick in slot 3 = 512MB in channel 2.

My concern is that I have read where getting any two sticks of RAM, let alone three sticks of RAM to work in dual channel can be tricky. In my initial post, I tried to match up the 256 and 512 sticks as best I could. Both new and old sticks are 2700C2 and both have a command rate of 2T.

I was just hoping somebody actually tried this and would say...yup...that should work just fine...


Or...somebody tried something similar and would say, don't do it or you will be wasting your money...

 

[gimpycow]

Overall though, yes it is possible.....will it work for you?....well that's somewhat of a gamble. Only one way to find out though

Yeah...that is the decision I have to make. And if it doesn't work...do I then return the memory + shipping + restocking fee or buy another stick of the exact same memory and hope that it works.

If you could take a look at the specs of the 256 sticks and the 512 stick. They are both Corsair XMS memory and all of them seem to be about the exact same thing...just different sizes. Would you agree with that? If so, maybe I should try. I have wasted money on worse things...

 

[Megadeth2]

The only board that I can think of that might run three sticks in DC is this one.

http://www.newegg.com/app/viewProductDesc.asp?description=13-128-246&depa=0

 

[gimpycow]

Mega,

Why do you say that, because it has 6 DIMM slots or something else?