[Solved] 6 GB Single Channel vs 4GB Dual Channel

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=N82E16820145269]

(b) Corsair Dominator GT 2x2GB (this will run in dual channel) [http://www.newegg.com/Product/Product.aspx?Item=N82E16820145268]

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.

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.

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?

Toms did an article recently. I just found it.

http://www.tomshardware.com/review [...] 264-3.html

Notice the massive difference between 3, 6 or 12Gb of RAM? lol
4Gb is a perfect number at the moment I reckon.

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.

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)

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.

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

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.

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.