12GB DDR3 Dual Channel Possible?

Hello guys,

This is my first post on these forums, so I hope I made this post in the right place.

I've been doing research into buying a new laptop. Right now I am looking at the Sager NP9150. Many resellers have the option for 12GB memory. However, some of these specify Dual Channel with 3x4GB. Based on extensive browsing on the web, I am not sure if this is possible. As far as I can tell, to enable dual channel, one needs an equal amount of memory in each channel. Thus, it is possible to achieve dual channel with three sticks (seen on some desktops). However, DDR3 does not function with mismatched units.

I've looked at various resellers of the Sager/Clevo NP9150, and some of them list the 12GB option as Dual Channel while others do not.

Can someone confirm if 12GB Dual Channel is possible?

Below are some options from resellers' websites for the 9150. The italicized option is the 12GB one in question.

Xotic PC
8GB - DDR3 1600MHz Dual Channel Memory (2 SODIMMS)
12GB - DDR3 1600MHz Dual Channel Memory (3 SODIMMS)

Gentech PC
8GB DDR3 1600/PC3 12800 Dual-Channel (4G X 2)
12GB DDR3 1600/PC3 12800 Dual-Channel (4G X 3)

Sager
8GB Dual Channel DDR3 SDRAM at 1600MHz - 2 X 4GB **
12GB DDR3 SDRAM at 1600MHz - 3 X 4GB

Powernotebooks.com
8GB (2x4GB) DDR3/1600 Dual Channel Memory Standard
12GB (3x4GB) DDR3/1600 Memory

Malibal (No mention of any dual channel)
(8GB) 8192MB, PC3-12800/1600MHz DDR3 - 2 SO-DIMM
(12GB) 12288MB, PC3-12800/1600MHz DDR3 - 3 SO-DIMM

Thanks,
Josh

 

It is extremely rare but I think it is possible.
Dual Channel does not necessarily need matched modules. Intel's Memory controller has a feature called FleX memory which allows mismatched units to operate in what is known as Asymmetrical dual channel. Basically, the access is interleaved between the banks so performance is better than Single Channel but worse than Symmetrical Dual channel.

Now the following is my understanding and is in no way gospel
As for the 12gb configuration, I believe it is possible bit it will be operating in Asymmetric mode.
The CPU basically has 2 RAM channels (64bit width each) that can support 2 banks each (each bank shares the channel's bus). The manufacturer probably enabled 2 banks for Channel 1 and only 1 bank for Channel 2. So basically, Channel 1 has effectively got a higher capacity potential than Channel 2 but the whole operation is Asymmetric if all banks are filled.
I would be interested what would happen if you filled Channel 1 with 2x4gb sticks and Channel 2 with a single 8gb stick...

 

Yes it is. There is no doubt and I do not care what anyone else says. I have it tested and proven for 4 generations back.

But let us consider or explain. Intel calls it "Flex Memory". We have other names but regardless the concept is simple. What ever RAM can match up or pair would run in what you kids call dual channel. Or I could say true dual channel. So with 12GB RAM I only see 8GB pairing/matching. So you have 8GB in "true" dual channel. The other 4GB is in single channel.

If we accept what I have said, which you kids better. We have 8GB DC and 4GB SC. How do we stand? OK we stand very good. The most requested data migrates toward the front and that would be the paired RAM. So consider 12GB is 8GB dual channel and 4GB single. So 8GB alone would start using anything above 8GB on drives. On a 12GB set up we have a 4GB buffer. What is better? Drive or 4GB? 4GB single channel would be way faster.

12GB is dual channel and better than 8GB. If anyone on this site says different they are morons.

Good luck.

Edit: Marksman beat me I guess.

 

Yep it will be dual channel, just to reinforce to other's comments. There is a slight performance hit, like 5% compared to true dual channel (matched size and speed) otherwise it's close enough. Personally, RAM is so cheap I would just buy another 4GB module for 4x4GB.

 

Thanks for the fast response guys. I'll probably go with the 12GB knowing that 8GB are in dual channel. I hear that 16GB is overkill in may cases, but at least I'll have the option to add in another 4GB if I ever need it.

 

Just buy 8GB with laptop and on saved money buy another 2x4GB kit atermarket.

 

Buy your laptop with 8GB. Then buy another 8 or 16GB and throw it in there for 16GB or 24GB total! Honestly, RAM is so cheap these days, it would be foolhardy not to.

 

Thanks for the replies. I will probably just got with the 12GB. Its only 25$ more then the 8GB option for Xotic PC. The 16GB is an additional 25$ top of that, but I feel that money can be used for upgrading other components.

 

If that's the case, go with 8GB and add 8GB more later when you can pocket $50.

 

SOLD. I am replacing my 4GB with an 8GB for a total of 12GB. 8 running in dual channel and 4 in single. Thanks!!!

 

I'm about to do this. I have 4Gb in 1 channel and 4Gb in the second (Samsung Series 7 Chronos laptop). I am going to change the second channel to 8 for a total of 12Gb. If CPU-Z still shows dual channel memory...then I guess it works.

 

It does and it will.

 

Thanks for the support man. Sometimes people don't feel like replying, but it means something to me. I appreciate it.

 

I can confirm that Dual Channel works with different modules. While back I've upgraded my nx9420 and nc8430 from 2 to 3gb ddr2 memory. each having 2gb+1gb modules. Dual Channel operated in a way that it used up to 1gb from a 2gb stick and at the same time used entire 1gb stick. Meaning any operations that were done in first 2 gigs of availible memory were working in a dual channel mode. After memory usage went above 2gb the remaining 1gb of "free memory" on a 2gb stick would be used in a single channel mode.