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6 GB Single Channel vs 4GB Dual Channel

Tags:
  • Memory
  • Corsair Dominator
  • Dual Channel
  • Single Channel
  • Product
Last response: in Memory
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October 27, 2009 5:51:31 PM

I'm building a gaming rig with a Phenom II X4 965 on an Asus Crosshair III Formula. The socket AM3 only supports dual channel (no triple channel). So, my options for RAM are:

(a) Corsair Dominator GT 3x2GB (this will run at single channel) [http://www.newegg.com/Product/Product.aspx?Item=N82E168...]

(b) Corsair Dominator GT 2x2GB (this will run in dual channel) [http://www.newegg.com/Product/Product.aspx?Item=N82E168...]

More about : single channel 4gb dual channel

October 27, 2009 6:15:44 PM

I don't get the "single channel" thing. I think you are confused by the kit packaging. Its the same memory no matter which kit you buy it in....and in my opinion it is terribly overpriced.
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October 27, 2009 6:17:59 PM

If i run a pair of two identical drives on my motherboard, they run at dual channel. if they're not in pairs, or not identical, they run single channel.
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October 27, 2009 6:19:39 PM

4Gb dual channel.

I still run 2Gb dual channel on Windows 7, no issues yet.
4Gb is plenty for games, and the performance increase on running dual channel is quite high.

I'm also assuming you have a 64bit version of Windows. 32bit can only access the first 4Gb (and that includes video memory).
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October 27, 2009 6:23:21 PM

belial2k said:
I don't get the "single channel" thing. I think you are confused by the kit packaging. Its the same memory no matter which kit you buy it in....and in my opinion it is terribly overpriced.

Usually a triple or dual kit works out cheaper than buying the DIMMs individually.
Well it does here anyway.

Pretty sure the poster knows this.
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October 27, 2009 6:25:22 PM

yeah, I will be running 64 bit Windows 7. thanks for the answer, spidersweb.
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October 27, 2009 6:26:52 PM

in future, if I want to increase my ram, and install another identical dual channel kit (so I now have 4 identical RAM modules), will they still run dual (quad?) channel?
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October 27, 2009 6:30:18 PM

well it would be dual channel still, but twice as large.
This depends, some motherboards have trouble with this.

I just stick with a 2 DIMM only policy to avoid problems.
By the time you need it, either your CPU/Mobo will be out of date, or 2x4Gb kits will be a lot cheaper.

Depends what you're doing I guess, I have trouble validating more than 4Gb of RAM.
At work I'm on Vista 32, so 3.75Gb of RAM is all I have, and despite being Vista, and having a VMWare image using 1Gb of RAM, and about 10 programs open at once while developing, I still usually have quite a bit left over. Often I start other VMWare images, e.g. Windows XP with IE6 for testing web apps, still don't run in to RAM trouble.

At home, 2Gb Windows 7, haven't ran out yet, although with newer games I bet I'd be pushing my luck a tiny bit. Prototype sucked up around 800Mb I think.
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October 27, 2009 6:41:38 PM

haha, that was a good link. Clears up a lot of my doubts. 4 GB should be more than adequate for now
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October 27, 2009 6:45:34 PM

I don't think either of you have the correct understanding of how Ram works. Dual channel simply means that the ram needs to be matched in each channel. If you put in the third ram from a triple channel kit for 6gb of ram, it does NOTHING to adversely affect the performance, and it is not now "single" channel. The whole channel thing is simply how kits are sold to match the available dimm slots on motherboards. As far as if you need 6gb or not, I can't say. It depends on how you use your computer, your video card, how intensive your multitasking is, and something people leave out often HOW OFTEN YOU RESTART YOUR COMPUTER. I have 6gb of ram on one of my computers, and often I'm using every bit of it after an extended session and after my antivirus has run, and have to restart to free up system resources.
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October 27, 2009 6:48:02 PM

Wrong.

Irrelevant of how kits are sold, putting two matched DIMMs in the correct sockets and enabling Dual Channel mode gives a massive increase to memory throughput.

I recommend reading this: http://www.hardwaresecrets.com/article/133/2

Switching to dual channel mode on your motherboard doubles the data width.
With 3 DIMMs, his motherboard will go back to single channel, allowing data to be only read from one DIMM at a time (instead of two).

And it sounds like your Windows install is a total mess belial. Even on this year old Vista32 install I don't run out of memory, I reboot weekly.

Quote:

On systems supporting dual-channel technology, the memory data bus is expanded to 128 bits. This means that on such systems there are 128 wires connecting the memory controller and the memory sockets. These wires are labeled D0 thru D127. Since each memory module can only accept 64 bits per cycle, two memory modules are used to fill the 128-bit data bus. So for dual-channel technology to work you need to have an even number of memory modules on your system (assuming that your AMD CPU or Intel chipset support this technology, of course). If you install just one module this technique won’t work because memory will still be accessed 64 bits per cycle. In other words, dual channel works by accessing two memory modules in parallel, i.e. at the same time.
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October 27, 2009 7:15:46 PM

I have never personally used an odd amount of memory, but it has always been my understanding that the first channel set will address that memory as dual channel, and the "odd" dimm will then be addressed individually...meaning there should be NO loss in performance from this configuration. As I said, I've never done it, so if anyone has please report back.
Vista 32 is better for not hogging memory...64 bit can and will use more memory, and hold on to it. That is why I always suggest at least 4gb for a 64bit install. Plus I multitask like an idiot and will have 3 to 4 memory intensive task running at the same time. Once my antivirus runs early in the morning, over 50% of my memory is usually in use by the system. I don't like to use the computer without more than 50% of ram available, so this usually results in a reboot. I used to run vista 32 on the exact same system, and I could go a long time without the reboots and without random system problems...but since I've switched to windows 7 64 this is no longer the case. And the install is pretty fresh, so it is not a clogged system (plus I keep my installs very clean and run cleaners regularly)
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October 27, 2009 7:25:25 PM

Well, sorry to the OP for posting bad info. Never too old to learn. As I said, I've never done it in a build, thank goodness. A long time ago I had read some bad info on the subject and it stuck with me. I always thought the "odd" module was addressed individually and did not affect the full channels mode of operation.
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October 27, 2009 7:32:36 PM

no harm done
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October 27, 2009 7:42:21 PM

Good on you for replying belial2k.
As you said, it's a learning thing. I make mistakes quite often, and rely on the veterans to whoop my ass. Plus it's somewhat fun to debate tech stuff.

I actually misread your post, ehehe came back to apologise for the misread, I went on a 'dual channel is better than single channel' rant rather than a 'you cant run double channel mode with 3 DIMMs' rant. Only covered the last part by fluke lol
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October 27, 2009 9:14:56 PM

also from the earlier post..

vista caches files into memory to use up spare memory... its called superfetch

even if vista says your memory is 75% used(or more) it will just ditch some cached files and give the memory to programs.. you arent really using 6gb.
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a b } Memory
October 27, 2009 9:18:24 PM

rand_79 said:
also from the earlier post..

vista caches files into memory to use up spare memory... its called superfetch

even if vista says your memory is 75% used(or more) it will just ditch some cached files and give the memory to programs.. you arent really using 6gb.

That's true. People not understanding how Superfetch works was a main cause of Vista's reputation of being a "RAM hog". If people had understood how the RAM was being used and that it would be freed up for use if needed they might not have bagged on Vista so bad.
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October 27, 2009 9:25:57 PM

I agree...as I said, I never had a problem under vista 32, The memory problems started when I went to 7 64 bit. After it hits 50% memory usage I start having random errors from programs not starting correctly. Anything that is already running still runs fine, its just opening new things that cause the errors....reboots always solve the problem, so I'm blaming it on low system resources. If I wasn't so used to leaving my computer on 24/7 for days at a time it would not be an issue, but now I pretty much have to reboot every day. This is only on my "work" computer at my shop that I always have a huge workload of several things going on at once on...my home "play" computers with similar configurations don't have the same issues.
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a b } Memory
October 28, 2009 1:52:14 AM

SpidersWeb said:
Irrelevant of how kits are sold, putting two matched DIMMs in the correct sockets and enabling Dual Channel mode gives a massive increase to memory throughput.

Actually, dual channel does increase memory bandwidth, but very few real world applications benefit from it. You can find several tests of single channel v. dual channel performance showing very little performance benefit, except of course in synthetic memory bandwidth tests. There are some applications (very few games) which are especially sensitive to memory bandwidth, but these are an exception, not the rule.
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October 28, 2009 1:58:08 AM

Yeah theoretical versus practical.
I've only seen synthetic memory benchmarks on memory.
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December 28, 2010 1:55:18 AM

sorry to bring this topic back to life.....

but if "dual channel does increase memory bandwidth, but very few real world applications benefit from it. "

is it safe to say that running 3 dimms of 2gb (total of 6gb) in single channel is still better than 2x2gb (4gb total) in dual channel?
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