murrayman wrote:

I'm looking to max out my RAM to 16gb, but when I peruse eBay, all I find are modules of "AMD only" DDR2 -- which sounds fine at first, since I have an AMD. But half the listings specify you must have an AMD chipset, not just CPU, in order for the memory to work.

Why would this be a problem? Your board has AMD chipset.

That memory is colloquially known as "High Density Memory". Finding exact information isn't exactly easy. What I have pieced together over the years is, that the memory uses a similar organisation as registered memory (the server kind, just without any buffering) and that is possible because the AMD memory controller is more flexible in the ways it can address memory than the intel one.

That is where the good news end. The bad news is, that the compatibility is, lets say, questionable. It won't work in all motherboards, it seems to be dependent on some form of bios support, or rather some omission of bios limitations (as I said, concrete information is virtually non existant). The memory is out of spec for normal memory standards and only works because of some peculiarities of the AMD memory controller. It seems Asus boards seem to be the least compatible or, depending how you want to see it, the strictest adherents to the actual standards.

It *might* work in your motherboard, it might not. The only way to know is to try it. If you are up for gamble go for it, just be aware that there are no guarantees it will work. But then, that is pretty much the only way to get 16GB unbuffered DDR2 and the memory is rather cheap.

All that being said, they are NOT a scam, just a liberal interpretation of the standards.

Koltoroc wrote:

That memory is colloquially known as "High Density Memory". Finding exact information isn't exactly easy. What I have pieced tog […]
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That memory is colloquially known as "High Density Memory". Finding exact information isn't exactly easy. What I have pieced together over the years is, that the memory uses a similar organisation as registered memory (the server kind, just without any buffering) and that is possible because the AMD memory controller is more flexible in the ways it can address memory than the intel one.

That is where the good news end. The bad news is, that the compatibility is, lets say, questionable. It won't work in all motherboards, it seems to be dependent on some form of bios support, or rather some omission of bios limitations (as I said, concrete information is virtually non existant). The memory is out of spec for normal memory standards and only works because of some peculiarities of the AMD memory controller. It seems Asus boards seem to be the least compatible or, depending how you want to see it, the strictest adherents to the actual standards.

It *might* work in your motherboard, it might not. The only way to know is to try it. If you are up for gamble go for it, just be aware that there are no guarantees it will work. But then, that is pretty much the only way to get 16GB unbuffered DDR2 and the memory is rather cheap.

All that being said, they are NOT a scam, just a liberal interpretation of the standards.

This is what I needed right here, unless anyone else has extra input. Thanks so much! If I give it a shot, I'll report back, at the very least to confirm one Gigabyte motherboard's compatibility / incompatibility. I've already looked around for relevant info for my mobo and Gigabyte in general, thinking perhaps someone else had tried this. Unfortunately I wasn't able to find a concrete answer.

Yeah, sounds familiar. I've been toying with the idea of getting a kit for my AM2 boards, but I'm somewhat gambling averse and tend to always have something better to spend my money on. It is precisely this lack of information that ultimately made me avoid them so far. I'm looking forward to reading about your experience.

Koltoroc wrote:

Yeah, sounds familiar. I've been toying with the idea of getting a kit for my AM2 boards, but I'm somewhat gambling averse and tend to always have something better to spend my money on. It is precisely this lack of information that ultimately made me avoid them so far. I'm looking forward to reading about your experience.

There was one person who left an eBay review on the one I linked above; used them in a Asrock K10N78D mobo with a Phenom II x4 955. It worked, but the timing and freq listed for the RAM was incorrect, so they had to manually enter the values in the BIOS; they got it to work at 5-5-5-15 timings @ 266mhz. This sounds like a potential performance bottleneck not worth dealing with just to have an extra 8gb. Would I be right in assuming as much? If so, I might opt to go the safe route an just get a set of 4x2gb for 8gb (currently running 4gb, so looking to go up either way).

not necessarily. Memory speed is generally not quite as important as it is made out to be with some exceptions (ryzen for example) You will get measurable differences, but not notable ones. Extra memory tends to make up for less speed.

Koltoroc wrote:

not necessarily. Memory speed is generally not quite as important as it is made out to be with some exceptions (ryzen for example) You will get measurable differences, but not notable ones. Extra memory tends to make up for less speed.

Understood. There seems to be differing opinions on this elsewhere, but in line with what you said, it seems to mostly come down to those who favor the numbers over general performance.

Decided to take the gamble; just ordered a set. Will post when I get them in and test them. They're coming from China (as they all seem to source from), so will be a little while yet.

I got some 4GB DIMMs working stable on a ASUS M3N78-VM Geforce 8200 board, but on a Gigabyte MA78GM-S2H 780G board they were not stable. It could be the board or hey maybe the Phenom IIs were different steppings or something like that.

The ASUS M3Ñ78-VM with Phenom II 940 has been running that 8GB setup for years now.

As far as i know the DDR2 modules for the older amd setups (cpu's, not chipsets specifically) used 1.8v while a lot of Intel setups require 1.5v

1.8v modules are far from stable on Intel platforms as the (on die) memory controller can not provide the required power stable. Don't know anything about the density part...

A few years ago i tried 2 sticks of 1.8v DDR2 Corsair modules on an Intel Core2Quad setup and it was not stable, even at a much lower fsb and memory speed.

DDR2 standard voltage is 1.8V. There is overclocker memory that requires as high as 2.2V but that is outside spec, If your system does not run with 1.8V memory something is wrong with it.

DDR3 is 1.5V for normal memory and 1.35 for Low Voltage memory. There is no Low Voltage version of DDR2

The full set of standard voltages of DDR memory typses is 2.5V for DDR, 1.8V for DDR2, 1.5 for DDR3, 1.35V for DDR3L and 1.2V for DDR4. Only DDR3 has a specified Low Voltage version.

I recently tried 4GB (2x2) of this AMD only DDR2 in my Asrock 4coredual-vsta (with a core2 e4300@2.4GHz) board and it seems to work fine.

I tried some of the cheap "AMD only" sticks from Ebay. None of them worked in my AMD DDR2 boards. Buy with caution. I would almost label this as a scam.

Koltoroc wrote:

DDR2 standard voltage is 1.8V. There is overclocker memory that requires as high as 2.2V but that is outside spec, If your system does not run with 1.8V memory something is wrong with it.

DDR3 is 1.5V for normal memory and 1.35 for Low Voltage memory. There is no Low Voltage version of DDR2

The full set of standard voltages of DDR memory typses is 2.5V for DDR, 1.8V for DDR2, 1.5 for DDR3, 1.35V for DDR3L and 1.2V for DDR4. Only DDR3 has a specified Low Voltage version.

There was nothing wrong with it after i used 1,5v ddr2 modules and the 1,8v Corsairs worked fine much later in an AMD system. Maybe there was some other incompatibility but i couldn't get it stable at the time.

That cheap high density stuff also works with nForce-chipsetted Intel boards. I had 8GB of "AMD-only" memory working just fine on an Asus P5N-E SLI (nForce 650i) with a Q6700 processor.

I was actually surprised to receive a correspondence with the seller to check and make sure I had ordered the right product since it was labeled AMD only. The message read as such:

"...But i must kindly remind you that the memory ram is high density only fit for AMD chipset Motherboard, Does not work with any Intel chipset computers, please make sure of it. if you cannot be sure of it, please tell me your computer's model, we will check for you if this memory module compatible with your computer or not.

BTW, if your computer is brand new like Dell, HP. Lenovo, IBM etc. with AMD CPU, this memory CANNOT work well on it. If your computer is built by yourself with the AMD CPU chipset, then this memory will be compatible.

Waiting for your confirmation.Then we can ship it to you ASAP..."

I sent them the model of the mobo and processor, and they didn't appear to have it on file, though they did offer to both help and take the memory back if necessary. So I'm going to be a guinea pig for both them and others I suppose. 😅 In any case, it doesn't sound like they have too good a technical grasp on the issue either -- that, or this (most likely) is just a broadly generalized way of addressing the issue with most buyers. I didn't try to get into details with them since this is, after all, an overseas seller, but I will be curious to see what comes of all of it.

From what I learned these days I reckon the key to success is signal strength.
The listed module has 16 K4T2G044QQ chips. I couldn't find the datasheet of the chip but I found the datasheet for the FB-DIMM module that uses this kind of chip. It's a 512M x 4bit chip in "Dual-Die Package", which means it's essentially two 256M x 4bit dies wrapped into one chip. So equivalently one of this "AMD-only" module has 32 256M x 4bit chips. I checked some universal unregistered 4GB modules and they have 16 256M x 8bit chips. I reckon the extra wiring on 32-chip modules induces more signal degradation and it won't work with chipsets and boards that have weak driving strength. I also checked some 4GB modules with 32 256M x 4bit chips made by reputable manufacturers and they are either registered or fully buffered, which are designed to mediate the signal strength issue.
I also googled the model number of the module, M395T5160QZ4-CF7, but couldn't find an exact match. The datasheet cited above suggested that a very similar string, M395T5160QZ4-CF76, corresponds to an FB-DIMM module. So if I am allowed to make a wild guess, the manufacturer unsoldered memory chips from recycled FB-DIMM modules and assembled them into unregistered modules.

I've seen some motherboards that allow the DRAM driving strength to be adjusted in the BIOS setup. Is this a case you could use that setting for?

I have purchased AMD only RAM before with no issues on ebay. The only issue you will have is most DDR2 AMD motherboards (chipsets) have an 8GB RAM Limit and you need to make sure the board you are going to use 4x4GB DIMMs on will do 16GB of RAM.

To be honest I have had more issues with Intel boards being very picky about RAM then AMD.

I found this proported blurb quoted from an OCZ. I wish I had a better source with less marketing wank, maybe someone else will have more luck:

"
With 11 column address bit support by the AM2 memory controller, the number of addresses in each row or page can be as high as 2048 individual entries for a page size of 16kbit. Unlike modules based on standard 10-bit column address chips with an ?8k? page size, the new Titanium AM2 Special modules take advantage of the AM2 controller?s feature set and provide a single rank solution with 2GB density using ?16k? pages. This allows the controller to stay ?in page? twice as long compared to standard memory architectures, thereby achieving unparalleled performance.
"

I bought some random ebay "AMD only" DDR2 a while back (not the OCZ) to try and get a Dell Dimension C521 we found in the trash working again. The good news is that it does work, but I never could get the machine stable long term.

BUT that PROBABLY is the machines fault than the memory I think. I never knew about the "AMD chipset" requirement - the C521 is an nVidia chipset - but it still would post and run with this memory. I suspect the reasons it didn't work for more than a few days were that the BIOS may have been allocating resources in a way that assumed there would never be over 4GB in the machine.

It also probably didn't help that the opteron we shoved in there wasn't really supported either... and the machine would still fall over with just 4GB in it. Sometimes you win, sometimes not so much.

If you can get this memory dirt cheap it might be worth to play with, I think I paid like $20 shipped for 8 sticks! so honestly I was surprised it worked at all.

The sticks I got were low profile, labeled "2GB DDR2-800 1.8V DDR2 PC2-6400U"

The memory chips:
SEC 225 BCE6 K4T1G044QF

Which when I looked those up are only rated for 333. I actually reflashed the SPD's to more lax timings trying to get them stable on the Dell, but it didn't really help.