Thinking of Adding Memory? Read Here First!

[specmike]

We have published a new application note that covers a few of the basic memory upgrade questions that are asked daily.

CORSAIR AN806: Memory Uprade Resource Guide

[jrefronc]

Very interesting, but, me being the rabblerouser that I am, I cannot keep this quiet:

In all of the Q&A and all of the basic "support" that is supposedly intended for entry level users -especially the fact that this information is targeted to upgrades (from 1 to 2 gig memory) why does Corsair not ever mention that adding 2GB modules to a system that already has 2GB modules (for a total of 4GB) is almost never possible since batches of ddr2 that do not come paired -even if they are the exact same model number and the same specification- are not compatible? I recently ate $200 because I was misled to believe that the same modules would be compatible. This is not the case. Why does Corsair not explain this phenomenon in plain English for its clients on page one?

A few Google searches with the right keywords will prove my point. I won't bother adding links (or screen shots of BSODS) to prove my point.

[ctal]

Originally Posted by jrefronc

Very interesting, but, me being the rabblerouser that I am, I cannot keep this quiet:

In all of the Q&A and all of the basic "support" that is supposedly intended for entry level users -especially the fact that this information is targeted to upgrades (from 1 to 2 gig memory) why does Corsair not ever mention that adding 2GB modules to a system that already has 2GB modules (for a total of 4GB) is almost never possible since batches of ddr2 that do not come paired -even if they are the exact same model number and the same specification- are not compatible? I recently ate $200 because I was misled to believe that the same modules would be compatible. This is not the case. Why does Corsair not explain this phenomenon in plain English for its clients on page one?

A few Google searches with the right keywords will prove my point. I won't bother adding links (or screen shots of BSODS) to prove my point.

If I'm understanding your post correctly, you're saying that it is "almost never possible" to purchase two sets of 2 x 1gB DDR2 that are the same model number, install the four memory modules in a mobo, and have them operate properly. If that is what you mean, I'm sure there are countless people (including me, on my present system) who could cite experience where that was done successfully.

On the other hand, I have seen lots of reports by people having problems trying to run four sticks of memory in various mobos, while finding that two sticks worked ok. I think it's hard to provide a general characterization of these reports, but I suspect they are as much mobo-related as memory-related.

Regards,
-- Al

[ctal]

After making my preceding post, I read through the Corsair application note (which is really excellent in my opinion). It does address exactly what JREFronc is referring to, I believe, on the first two pages (the "number of memory modules used" and "overclocking" sections). It emphasizes that use of four modules may require bumping up the memory controller voltage (the voltage to the northbridge in Intel systems, which only some mobos allow to be adjusted), and that overclock capability may be reduced when four modules are used, again due to memory controller (not memory) limitations. And that mobos that provide marginal cooling for the northbridge may not be able to handle having four memory modules on the board.

Excellent application note, SpecMike!

Regards,
-- Al

[Baud]

CTAL, I agree with you on the fact that lots of people use 4 x 1GB modules without trouble. But I believe he's talking about 2 x 2GB modules, which run OK on my Asus Maximus Formule (the make is OCZ, and I don't know if the article he's reffering to is Corsair specific).

I had trouble running the same memory on an Asus P5KC, and the problem disappeared by RMAing this MB.

[Sir Skully]

I've run 8gig of Corsair XMS2 with Visita 64, oc'ed. This is on a Gigabyte EP35-DS4 mobo. I can oc the 8gig as well as if it were 2gig, on this mobo. This has been and is one of the best mobo's I've owned. And believe me I've been through quite a few mobo's. This Corsair memory isn't to shabby either.

[jrefronc]

What I meant to say but apparently did not say clearly enough is that if you have 2x1Gb sticks and want to add two more at a later date (for a total of 4x1Gb) that are the same model but a different version they do not work well together. This happened to me with Dominator pc2 8500 (v1.1 + v2.0) and it took many many hours of scouring the internet to find anyone who actually talked about adding more of the same model number of a newer revision. I eventually found (and subsequently lost) a site that explained this phenomenon.

Apparently this is the very reason DDR2 is sold in "Matched Pairs..." Because when you take a pair from a different manufacturing run and put it next to an older pair -even if they are the exact same model number- you can and probably will have issues. Neither voltage nor mobo had anything to do with it from what I could find.

The best answer I got was to replace the old 2x1Gb with 2 new 2x2gb. If you want four sticks, but don't get those four sticks at the same time from the same manufacturing run you can forget about DDR2 stability.

If I am completely off base here I'd love to hear about it.

End of line.