Gigabyte says AMD CPUs dont work in dual channel mode - GA-MA78GM-S2H

[Sectoid]

Hi All,

I've bought and assembled for my brother an upgrade based on these specs:
Motherboard : GA-MA78GM-S2H(rev.1.1)
BIOS Ver : F7
VGA Brand : HIS Model : Radeon 4670 IceQ
CPU Brand : AMD Model : Phenom X4 9550
Operation System : Vista 64-bit SP : 1
Memory Brand : Kingston Type : DDRII
Memory Size : 2 x 2048mb Speed : 800mhz
Power Supply : Seventeam 420 W
HDD: Seagate 500GB SATA II

Only the power supply, case and dvd-rw drive were kept from the old rig.

The motherboard came with the F5 BIOS. There, I could change the "DCT" (where DCT stands for Dual-Channel Type, I figure) option from "unganged" to "ganged". Besides this option being hidden, as you could only see it if you set memory timings to "manual", after upgrading the BIOS to version F7 (latest), the option was gone and the memories could only be run in single-channel mode (or "unganged").

Since I did not find anything about this on the web (not true, I found a guy asking about this at the AVS forums but no one answered him), I sent a message to Gigabyte support:

Sent : 2/17/2009 20:51
Question : Hi, before bios F7 I could choose dual channel mode by changing the DCT option to "ganged". After the update to F7, the DCT option is gone and I'm only able to work in single channel mode (unganged). Please release another bios file that corrects this! Thank you.

Their reply came as this:

Answer : Dear Carlos,

Thank you for your kindly mail and supporting GIGABYTE. About the issue you mentioned in your earlier mail, due to CPU manufacturer recommends to close DCTs Mode function, thus, this option is no longer in the new version of BIOS, the deafault setting of DCTs Mode is Unganged Mode.

However, our engineers have tested these two features, the performance of Unganged Mode and Ganged Mode are almost the same, thus, it would not affect any performance on your motherboard. Sorry for the inconvenience.

At last, if you still have any further question to this issue or suggestion about our products/service, please do not hesitate to contact with us. If you have any issue different from original, make sure you issue a new form in order to get proper assistance and it may be response faster as well. We will try our best to help you resolve the problem ASAP.

Best Regards,
GIGABYTE TECHNOLOGY

Now then I ask you: have I missed the news about this and are they right to say that AMD recommends that their CPUs do not be run on dual channel? I sent them the following reply:

Sent : 2/18/2009 23:05
Question : Hi,

I'm sorry but I do not agree. I'm a computer engineer myself and it's been proved that dual channel mode makes difference.
In all common sense, it's strange to say otherwise, since you're doubling the memory bandwidth, going from 64-bit to 128-bit.
Worse is that the board and CPU were marketed as dual channel capable, but with this modification, they aren't. What you're saying to me, in your sentence "due to CPU manufacturer recommends to close DCTs Mode function" is that AMD informed you that their CPUs aren't stable when in dual channel mode. This cannot be correct, since various other motherboards make AMD CPUs work this way, and they work flawlessly. If it was the way you said, it would be a major flaw in AMD's design, worthy of newspapers.
I do expect another solution for this, and I'll create discussions about it at anandtech.com and other sites.

Thank you,

Carlos

They just sent me a "*** off" reply:

Answer : Dear Carlos, Thank you for your kindly mail and supporting GIGABYTE. About the issue you mentioned in your earlier mail, the DCT mode option you mentioned is asked to removed by AMD, so this option will be dispeared in future released BIOS, and the memory will runs in unganged mode by BIOS default. If you still want to use this option, we suggest you can use the previous F5 BIOS, sorry for the inconvenience. At last, if you still have any further question to this issue or suggestion about our products/service, please do not hesitate to contact with us. If you have any issue different from original, make sure you issue a new form in order to get proper assistance and it may be response faster as well. We will try our best to help you resolve the problem ASAP. Best Regards, GIGABYTE TECHNOLOGY

Can anybody help me with this? Is it really true that AMD is recommending that motherboard suppliers prevent users from using dual-channel mode? Or is Gigabyte just covering some flaw and blaming AMD?

 

[mpjkraak]

seems kind of @ssbackward but for me to turn on 64bit processing I have to set UNGANGED to ALWAYS otherwise AUTO.
Memory config is not in the same menu. That's Bank interleaving/Channel interleaving & CLK to all DIMM Y/N.

Have an ASUS mobo (crappy but) M2N-VM DVI.

Good luck !

 

[FireTech]

Originally posted by: Sectoid
Can anybody help me with this? Is it really true that AMD is recommending that motherboard suppliers prevent users from using dual-channel mode? Or is Gigabyte just covering some flaw and blaming AMD?

Contact AMD and ask them?

 

[Sectoid]

You know, I didn't even think about this
Probably I'll just get another automatic reply, but it's worth a try.

 

[Flipped Gazelle]

The whole "ganged" vs "unganged" is kind of weird. Ganged mode is dual channel, but unganged is not exactly the traditional single channel mode. It's been my experience that "unganged mode" results in superior performance.

EDIT: here's a good explanation, look about 1/3 down the page: http://ixbtlabs.com/articles3/...ield-phenom-page1.html

 

[tcsenter]

Originally posted by: Sectoid
The motherboard came with the F5 BIOS. There, I could change the "DCT" (where DCT stands for Dual-Channel Type, I figure) option from "unganged" to "ganged".

DCT = DRAM Controller

IIRC, the change was to remove manual selection of the DRAM controller mode. It should still enable dual channel by population rule. And yes, even AMD says unganged mode is the better choice unless you need ECC support:

2.8.4 Ganged or Unganged Mode Considerations

Typical systems built from multi-core products benefit from the additional parallelism generated by using the two DCTs in unganged mode. Single core products or products that require additional ECC correction capabilities should implement ganged mode. -- BKDG for AMD Family 10h Processors

Dual channel is largely irrelevant except in particular application usage scenarios.

 

[Sectoid]

Thank you all for the help, though I'd already been given the explanation by an AMD forum user.

Just to sumarize for future reference by other people, Phenoms have two 64-bit memory controllers. Ganged mode makes them work together as if they were a single 128-bit controller. Unganged mode makes them work separately as two independent 64-bit controllers. In mono-threaded applications, ganged mode may perform better, but as applications become more threaded to make use of multicores, unganged mode should provide the best performance.

I was totally wrong in my assumption that the dual-channel concept remained the same, and I've been unkind to the Gigabyte spokesperson. It's a very easy to misunderstand concept though, specially when you think about the previous stablished concept and about people who don't follow all technology that much up close.

I really liked a quote I read somewhere else:

Im going to push all the motherboard vendors I talk with to reword unganged single channel to dual channel 2x64bit mode on the boot screen, this simple misrepresentation is going to cause no end of RMA requests for all the memory manufacturers.

I want to thank you all for the help again, I've always counted on these forums for the worst problems and was never let down.

 

[SunnyD]

Ironically, if you look at the memory info in CPU-Z, you'll notice it says "Channels: Dual Channel", "Mode: Unganged".

I asked myself this as well for a while, then decided not to care.