Limitations of the Athlon64 939 memory controller

[flawlssdistortn]

Hey guys, many of you are probably aware of the numerous stability problems people have been experiencing when trying to run dual channel DDR400 on socket 939. I myself built the system you see below over the summer, and since then struggled to attain a stable configuration. I've participated in many threads and called Gigabyte and AMD numerous times to try and get to the bottom of the issue. None of the answers I recieved from either company was consistent or anything other than vague.

Hopefully you guys can help me sort all this out. Here are my questions...

Does AMD guarrantee the 939 memory controller to run dual channel at 200Mhz? Is this limited only to single sided RAM, rather than double sided RAM? What appear to be the extreme limits in terms of frequency, timings, and command rate, depending on the number of modules used?

How much influence does the motherboard have in memory stability, now that the memory controller is integrated on the CPU? Does this influence reside in the BIOS, or would it be in the physical characteristics of the board?

Thanks in advance!

 

[Peter]

Yet again: Unbuffered PC3200 is _specified_ (by JEDEC, the standardizing comittee for these things) to work with one DIMM per channel. It may be double sided alright.

Mainboard layouts should never do worse than what this specification demands, but apparently some aren't quite up to it. They may of course do better, and let you still run 200 MHz with two DIMMs on each channel. Relaxed timings will be in order for this nonetheless - command rate is the first thing to step up to 2T.

Early Athlon-64 steppings (B3, maybe also C0) could not run 2T command rate; none of these are even available on socket-939 though.

 

[Gamingphreek]

I dont know what "problems" you speak of but seems to run flawlessly in most computers.

As far as a 2T command rate, well that is really only for 4 DS Dimms. Just running in DC does not require a 2t unless you are trying to OC to the max in which case it might help with a huge performance hit you have to overcome.

-Kevin

 

[flawlssdistortn]

I am referring to the fact that my motherboard seems to be unable to run dual channel DDR400 with almost all brands of memory. According to Gigabyte, and now Peter, AMD does not "guarrantee" this configuration even though most people are able to run it. Therefore my question is how limited (if at all) is the processor in this sense, and how have the motherboard manufacturers been able to work around it?

 

[Peter]

Listen. One DIMM _per_channel_. That makes two if you have dual channel operation. Four DIMM operation at 200 MHz is what's neither specified nor engineered to work.

If it doesn't work even with two identical DIMMs, one on each channel, then something's fishy.

 

[flawlssdistortn]

Ok, I get what you're saying - the standard does not support me running 2 identical 512MB DDR400 modules in dual channel. So let me ask how people are doing it? Every board is reviewed by running this config, and even 4 DIMMS at 200Mhz. All the manufacturers market their board as being able to support these configs. And it seems the MSI and ASUS don't have memory problems when mine does. So what did they do? What's different?

 

[sao123]

Ok, I get what you're saying - the standard does not support me running 2 identical 512MB DDR400 modules in dual channel. So let me ask how people are doing it? Every board is reviewed by running this config, and even 4 DIMMS at 200Mhz. All the manufacturers market their board as being able to support these configs. And it seems the MSI and ASUS don't have memory problems when mine does. So what did they do? What's different?

NO NO NO
The minimum standard is that any mother board will support up to 2 DIMMs (1 or 2) running in single channel mode (Channel A slot 1, or Channel A slot 1 + slot 2) whether the DIMM is single or double sided does not matter.

Also the minimum standard is that any mother board will support 2 DIMMs running in dual channel mode @ 200 Mhz (Channel A slot 1 + Channel B slot 1) whether the DIMMs are single or double sided does not matter.


What is not supported is running 4 DIMMS in dual channel mode @ 200 Mhz (Channel A slot 1 + Channel A slot 2 + Channel B slot 1 + Channel B slot 2) whether the DIMMs are single or double sided does not matter. This configuration will usually run @ 166 Mhz.
Certain AMD CPU's do will work at this operation (has nothing to do with the motherboard...as the memory controller is on the cpu), even though the specifications state it will not.

to the fact that my motherboard seems to be unable to run dual channel DDR400 with almost all brands of memory

Every motherboard maker publishes a list of memory that are certified to work with your system setup. you should stick to those guidelines. Some require unbuffered, some require registered memory.

 

[rgwalt]

Originally posted by: sao123
What is not supported is running 4 DIMMS in dual channel mode @ 200 Mhz (Channel A slot 1 + Channel A slot 2 + Channel B slot 1 + Channel B slot 2) whether the DIMMs are single or double sided does not matter. This configuration will usually run @ 166 Mhz.
Certain AMD CPU's do will work at this operation (has nothing to do with the motherboard...as the memory controller is on the cpu), even though the specifications state it will not.

Any indication as to what processors will run 4 DIMMS in dual channel mode?

Ryan

 

[sao123]

Any indication as to what processors will run 4 DIMMS in dual channel mode?

I hope you understand... the 2 blue slots are slots 1 of channel A and slot 1 of channel B. The 2 black ones are slots 2 of channels A & B. So...if you have at least 1 chip in channel A and at least one chip in Channel B...your running dual channel mode.) Therefore... Absolutely All 4 DIMM configurations are running in dual channel mode. (there is no 4 DIMM SINGLE Channel MODE. )

Now what the question is....is what speed do 4 DIMM configuarions run at?
Like i said...most will run perfectly well @ 166 speeds. IE - DDR 333 equilovent.

How many cpu's will run 4 DIMM configuarions at the full 200 Mhz? Thats akin to asking how well will my cpu overclock? (Stable or fry?) There is no particular pattern within various models or even batches, it jsut depends on how many defects exist within that particular chip. Some do, some dont. Its truely a 50/50 chance if yours will or not. Actually its more like 30/70 against it.

 

[rgwalt]

Originally posted by: sao123

Any indication as to what processors will run 4 DIMMS in dual channel mode?

I hope you understand... the 2 blue slots are slots 1 of channel A and slot 1 of channel B. The 2 black ones are slots 2 of channels A & B. So...if you have at least 1 chip in channel A and at least one chip in Channel B...your running dual channel mode.) Therefore... Absolutely All 4 DIMM configurations are running in dual channel mode. (there is no 4 DIMM SINGLE Channel MODE. )

Now what the question is....is what speed do 4 DIMM configuarions run at?
Like i said...most will run perfectly well @ 166 speeds. IE - DDR 333 equilovent.

How many cpu's will run 4 DIMM configuarions at the full 200 Mhz? Thats akin to asking how well will my cpu overclock? (Stable or fry?) There is no particular pattern within various models or even batches, it jsut depends on how many defects exist within that particular chip. Some do, some dont. Its truely a 50/50 chance if yours will or not. Actually its more like 30/70 against it.

I see... so if I add another 2 sticks of memory some day so that I have a total of 4, I will still be running in dual channel mode, but it will default to a lower speed?

Ryan

 

[sao123]

I see... so if I add another 2 sticks of memory some day so that I have a total of 4, I will still be running in dual channel mode, but it will default to a lower speed?

Correct.

 

[Peter]

Originally posted by: flawlssdistortn
Ok, I get what you're saying - the standard does not support me running 2 identical 512MB DDR400 modules in dual channel. So let me ask how people are doing it? Every board is reviewed by running this config, and even 4 DIMMS at 200Mhz. All the manufacturers market their board as being able to support these configs. And it seems the MSI and ASUS don't have memory problems when mine does. So what did they do? What's different?

Is this so hard to get?

Two DIMMs. Two Channels. One DIMM per channel. Within PC3200U specification.

 

[flawlssdistortn]

Well thanks for bearing with me. The reason I'm trying to straighten this out is because many people with my particular board can't get a stable dual channel DDR400 with even 2 DIMMS. One person contacted Gigabyte tech support and they said that AMD did not support 200Mhz at all in dual channel. So I guess Gigabyte is wrong, and is just trying to point the finger at AMD instead of owning up to their unstable board.

 

[eLeven]

Gigabyte just suks... I have the K8ns Pro and may have the same problem. I'll tell lyou when I get my ram... I'll never buy another Gigabyte product... I read the review and most other mobos have no problems running 2 sticks at 400mhz. I hear what you're saying. If mine wont run it then its going back to the store and I'm getting an Asus

 

[sao123]

Though this isnt the place for troubleshooting.....

It

(has nothing to do with the motherboard...as the memory controller is on the cpu),

Mind If i ask what cpu, memory, & motherboard you are trying to use?
Brand...Model...Speed...Size... (gimme all the details.)

 

[Peter]

Quality of the mainboard's layout is a lot to do with the results you get out of the RAM controller. True, with AMD64 architecture, it's in the CPU not the chipset northbridge, but mainboard layout makes a big difference to the better or worse.

 

[flawlssdistortn]

Does anyone know how the mainboard layout is able to influence memory stability?

 

[sao123]

Wait....Hold it... Stop.... Everyone back up.

Eleven....
If this (K8NS Pro A64 3200 6800GT) is your system specs... I have identified your problem...and is totally different than flaws.

You have a socket 754 AMD K8 3200 CPU. Since the K8NS is a Gigabyte Socket 754 Motherboard.

No socket 754 AMD cpu has a dual channel memory controller....ever. Dual channel DDR wasnt included in the AMD product lineup until the socket 939 processors. there is nothing wrong with your cpu, mobo, ram or anything.
I refer you to the AMD Website for proof. Take note that the socket 754 cpu lineup has 3.2 GB/s of Memory Bandwidth. The Socket 939 lineup has a 6.4 GB/s of Memory Bandwidth. This is the difference between single and dual channel memory system.
Also, take note of the Ga-K8NS Pro page which makes no claims of Dual Channel DDR architecture. In comparison with the Ga-K8NSNXP-939 page which specificially makes claims of Dual Channel DDR Architecture.



Now to flaw... here is the AMD list of approved memory configuration.pdf. I dont see Corsair anywhere in that list.
now dont get me wrong corsair is a quality memory vendor and lots of people use them, but im am very wary because you are claiming to be using value-ram, instead of their mainstream ram.

 

[StriderGT]

Originally posted by: eLeven
Gigabyte just suks... I have the K8ns Pro and may have the same problem. I'll tell lyou when I get my ram... I'll never buy another Gigabyte product... I read the review and most other mobos have no problems running 2 sticks at 400mhz. I hear what you're saying. If mine wont run it then its going back to the store and I'm getting an Asus

I think that Gigabyte had a fair share of problems regarding double sided mem modules:
Tom's tests

But reports on their new S939 nforce4 are good (Anand has reviewed it recently) and did not mention any serious incompatibilities.

 

[flawlssdistortn]

sao123, yes I've seen that document. But the motherboard manufacturers have been able to put out compatibility lists that are 3 times as long as that. Except Gigabyte, they never put one out officially at all. I also know that my Value Select is not good enough. However, there have been MANY complaints by people who have high end memory.

 

[sao123]

Actually, Im pretty sure asus took that list and re-published it as their own.