Memory Question?

[blizz]

I currently have 1GB of dual channel DDR OCZ premier ram in my asus a8n sli mobo. Would it work fine if i added a 1GB stick of ocz premier ram in addition to the two 512mb sticks i currently have running in dual channel?

[specmike]

Probably not, and if it does work, it won't work well. Most dual channel MOBOs won't work at all with 3 DIMMs loaded. They require 1,2, or 4 DIMMs. If you need to add memory, I would suggest 2 x 1gb and find another use for your 2 x 512mb. Or, you can add 2 x 512mb but, in some cases if you mix ICs or different revisions of memory, your system may be unstable or not even boot. It "probably" will but the only way to know for sure is to install it and test it.

[blizz]

Ah thats just what i was thinking. I will probley just buy a nice dual channel kit, and the same kit again in the future. Thanks for your help!

[Wolf Dog]

In a recent communication between myself and the folks at Crucial, this subject was discussed. I was told by them that in order for dual channel memory to function properly all sticks must be of the same density. In other words.

YES
1X512
1X512

NO
1X512
1X1024

NO
1X512
1X512
1X1024

[specmike]

Originally Posted by Wolf Dog

In a recent communication between myself and the folks at Crucial, this subject was discussed. I was told by them that in order for dual channel memory to function properly all sticks must be of the same density. In other words.

YES
1X512
1X512

NO
1X512
1X1024

NO
1X512
1X512
1X1024

The manual for the ABIT AB9 disputes this. And, I have seen many systems that can run some very odd combinations of memory. Some DC MOBOs won't even boot with 3 DIMMs. But, I have run an ASUS P4C800 Deluxe with a PC2700 and PC3200 (each with different ICs) mixed and gotten stable dual channel operation. So, the whole deal of mixing densities, ICs, revisions is a crap shoot at best. The only way to EVER know if it will work is to mix, boot, and test.

However, Crucial IMO makes a responsible reply. I would state the same as a Corsair rep because "IF" for some strange reason an odd mixture of memory I suggested does not work, then I am guilty of handing out bad advice. And there are some combinations that will not work. Ideally on a dual channel MOBO, ALL DIMMs will be the EXACT same with regard to density, ICs used, revision, PCB, etc.

[Wolf Dog]

Originally Posted by specmike

The manual for the ABIT AB9 disputes this. And, I have seen many systems that can run some very odd combinations of memory. Some DC MOBOs won't even boot with 3 DIMMs. But, I have run an ASUS P4C800 Deluxe with a PC2700 and PC3200 (each with different ICs) mixed and gotten stable dual channel operation. So, the whole deal of mixing densities, ICs, revisions is a crap shoot at best. The only way to EVER know if it will work is to mix, boot, and test.

However, Crucial IMO makes a responsible reply. I would state the same as a Corsair rep because "IF" for some strange reason an odd mixture of memory I suggested does not work, then I am guilty of handing out bad advice. And there are some combinations that will not work. Ideally on a dual channel MOBO, ALL DIMMs will be the EXACT same with regard to density, ICs used, revision, PCB, etc.

I am inclined to agree with what you say. I have found this to be correct when talking to certain tech folks at the manufacturer, and this confuses me or makes matters worse when I'm trying to figure on what to do for best performance.

Dual Channel memory is supposed to be backward compatible to the slower of the two modules if different speeds are used ( clock down), I think, but when I talk to the folks at Crucial they use words that can throw one off like "generally speaking" "In most cases" Casual talk with them they are more apt to say yeah yeah it will work, but when they email me it's a little different with the words.

Mixing the two different densities I think would work, especially if they were the same speed, but according to the email I recently received from Crucial they said not to mix the density or the speed in dual channel for maximum performance of the PC. So now I'm more confused than before I spoke to Crucial????? Probably best to examine the words used when talking to the tech folks at the manufacturer level.

As far as I'm concerned, for optimum and best performance of a dual channel PC, I would use matched pairs of DIMMS of the same speed and density, IMO.

An example of what I mean:

Yesterday I had a tech guy on the phone from Diamond, the video card people. I questioned him about an X1600 256 bit AGP 8X card he said they had as being incorrect, he insisted the card was 256 bit. I asked to speak to a supervisor and he also said this card came in 256 bit. When I got a little more firmer he decided to look in the book and he came back and said he was sorry and that the card was 128 bit not 256. Crucial is a fine company it;s just that some times you run across someone that may not be that well informed and in turn gives out the wrong information. Gotta keep asking questions I guess?

[specmike]

Well, Crucial gave a good answer IMO and I also believe you are totally correct here:

As far as I'm concerned, for optimum and best performance of a dual channel PC, I would use matched pairs of DIMMS of the same speed and density, IMO.

This is especially true in the case of 2 x 1gb vs 4 x 512mb, all other things being equal. If nothing else, you should get a superior OC with 2 DIMMs.

One of the major factors behind all of this mixing and matching is bios. In the past I have seen bios play a huge part in this. And, since every MOBO maker does it differently, it would be impossible for a memory company to test them all and test all potential memory mixture scenarios.

Safe answers:
Don't mix n match DIMMs.
Use 2 x DIMMS to achieve desired memory amount vs 4 x DIMMs to achieve the same memory amount.
MOBOs will OC better with fewer DIMMs.

[blizz]

Yea i guess im out of luck. I will just give my old ocz ddr 1GB dual channel kit to my brother, and tommorow I will go purchase a new 2GB dual channel kit. Thanks for the help guys!