Compatiblity problems: Single-sided vs. Double-sided DIMM

Question

Hello everyone, I just registered.
Short version:
I'm considering purchase of one of the following motherboards: G41M-P26, G41M-P21.
(the forum doesn't allow me to post links, even to MSI site )
My question: will either of them work with my two pieces of 2GB sigle-sided DIMMs?
Detailed version:
I've recently bought a motherboard (not an MSI product, different chipset then G41), but had to return it to seller, due to its memory compatiblity problem (details to follow). Now, I'm looking for another motherboard, so I need information BEFORE next purchase, so that the problem wouldn't happen again to me.
A bit of technical background. As I've just learned, memory modules have implicit parameter, called rank or row. It has nothing to do with timing. It's more like axis, or dimension. It has effect on how memory controller combines multiple memory chips on a DIMM into logical memory unit.
(again, the forum doesn't allow me to post links. I wanted to link to Wikipedia pages about "Memory Geometry" and "Memory Rank")
Usually, single-sided DIMMs are rank 1, and dual-sided DIMMs are rank 2. Therefore, rank can be guessed from how the DIMM looks. The only 100% reliable method, is datasheet from DIMM manufacturer. For example, "module organisation is 2R x 8" means it's rank 2.
Generally, a motherboard should work with any rank, as I guess, it's supposed to give DIMM manufacturer flexiblity to pick chip density. My problem with the returned motherboard seems like I've bumped into some really exceptional case.
Facts about the mobo:
- it had 4 DIMM slots, with max 2GB per slot limit.
- it did not work with single-sided 2GB DIMM.
- it did work with dual-sided 2GB DIMM.
My guess at explanation, is the mobo has some kind of limit of maximum memory per "row" it can address per slot. So that if you want to utilise full slot capacity, both "rows" must be populated. I believe if I had 4 pieces of 1GB single sided DIMMs, it would work.
Further guess at explanation, is that I happened to have bad luck, as I combined relatively old mobo (as it's LG775 obviously) with brand new DIMMs. Manufacturing densities are increasing over time, and in consequence typical DIMM organisation changed too.
Now, back to MSI.
I've looked into "memory test report" documents at MSI site, for each of the two MSI motherboards I mentioned in the beginnng. They contain list of DIMMs that were tested with these motherboards. I used DIMM product numbers to get datasheets from manufacturers, to learn what rank those DIMMs are. If I had found tested single-sided 2GB DIMM on the list, it would have confirmed that my planned purchase is safe.
The result is, I didn't find any 2GB DIMM that would be rank 1. Not a single one. All of 2GB DIMMs on the list are dual-sided! That's totally at odds with the current situation on the market, where single-sided DIMMs are the norm.
To sum it up, "memory test report" documents didn't provide information, that would be either affirmative nor negative for my question. I'm helpless.

Answer 1

Quote from: deadbeef on 27-September-12, 21:22:47
I'm grasping at straws here... It's confusing. I looked into G41 "supported memory" document for motherboard from different manufacturer (also G41 chipset, and 2 DIMM slots). It was actually an update, dated at 2012. There were listed few 4GB double-sided, as well as couple of single sided 2GB.
The Intel G41 Express chipset includes a dual (DDR2/DDR3) memory controller.
DDR2-667, DDR2-800, DDR3-800 and DDR3-1066 are supported.
8GB DDR3-1333 are NOT supported (because there is not enough bandwidth for them).
In "overclocked mode" (1333MHz) you are limited to 4GB RAM
Due to this dual memory controller, the G41 chipset supports up to the total of 4 ranks (4 sides in total) of RAM at max.
1R+1R+1R+1R or 2R+2R.
4 years ago (when G41 has been released), the single-sided 2GB (256x8) memory modules and the 4GB (256x16) memory modules were a "rara avis".
So with the "default" BIOS the chances to use them are close to zero.
You need to pick up a G-41 mainboard, to study the BIOS updates and to see if there is a "memory compatibility" update.
But better, contact MSI.
On the other hand, DDR3-1066 (CAS = 7) is not faster than DDR2-800 (CAS = 5).
So if you want 8GB, it's better to go with 4x2GB DDR2-800.
You can find some awesome & cheap Corsair kits (all of them with 128x8 double-sided IC's)