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8GB single channel vs 4GB dual channel

Last response: in Memory
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December 12, 2010 10:24:39 AM

Hello
This is what I have on my PC

8GB (2x4GB) RAM DDR3 @ 1600Mhz

4GB(2x2GB) RAM DDR3 @ 1333Mhz

in total, I have 12 GB of RAM
I can put them in

1) 6GB Dual Channel (4GB-2GB-4GB-2GB)

2)8GB Single Channel (4GB-4GB-X-X)

3) 4GB Dual Channel (4GB-X-4GB-X)

My main question is, which one is better?

What happens if I put RAM like this?
4GB-4GB-2GB-2GB

Will Windows recognize that as this?
2GB-2GB-2GB-2GB
and give me 4GB of Dual Chanel RAM?

Or will Windows give me the full 12GB of RAM (Single Channel)

Thanks for all your help, this is all very new confusing to me

I just kind of figured it out

a b } Memory
December 12, 2010 11:07:10 AM

1. You should put the same-sized modules in the same-color sockets. So if your RAM sockets are black-blue-black-blue, you should put them in 4-2-4-2 or 2-4-2-4 for the best performance.

2. If you put it in 4-4-2-2, It will run 2GB out of the 4GB modules in dual channel with the corresponding 2GB modules in the other bank, and the other 2GB will be in single-channel mode. So this is like "partial dual-channel".

In short, matching capacity = put in matching colors. That will give you the best performance. Although it has been proven by Tom's Hardware than single vs. dual channel doesn't really make a huge difference in real-world applications.
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December 12, 2010 11:22:21 AM

I would rather use
1) 8GB DDR3 @ 1600Mhz with CAS 9
2) 6GB DDR3 @ 1333Mhz in Dual Channel with CAS 7

If the second option is better, faster, and will make a big difference, please let me know

From what I see it, it's like SLI with RAM, something like that.
Not SLI, I mean it's like the Intel Core 2 Duo.
It's not the clock speed, it's the fact that there are two processors.

Can I say that running
4-2-4-2 will give me 6GB of Dual CHannel mode, which is SOMEHOW equivalent to having 12GB of RAM?

or not really?
From what I heard from you, it doesn't makes a big big difference

Right now, I am running 8GB DDR3 1600Mhz CAS 9
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a b } Memory
December 12, 2010 11:33:08 AM

I think you're misunderstanding dual-channel mode. Dual channel mode will interleave the memory so that your (theoretical) memory performance is doubled. For example, if one of your modules can do 8GB/s, and the other one can also do 8GB/s, then in dual channel, they can do 16GB/s. They will not, however, decrease the capacity of your total setup. So if you use 2x4GB modules, you will have all the 8GB available to your computer. It will not halve the system's memory capacity.

Yes, the memory speed and timings don't really affect performance much. Here is the Tom's Hardware article if you're interested. It was conducted in 2008, but it still holds true today: http://www.tomshardware.com/reviews/ram-speed-tests,180...

If you don't really need that much RAM, I suggest you just use the 2x4GB modules. However, if you want to use all of them, 4-2-4-2 will give you the best performance. It will let you use all 12GB of RAM (assuming you have a 64-bit OS) and will run in dual-channel mode. It will run in the speed of the slower module, though, so your 1600MHz 4GB modules will run in 1333MHz only. But in my opinion, the speed you "lose" is worth the increase in RAM if you really need the memory capacity.
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January 3, 2011 12:02:14 AM

Interesting article. Based on those results...basically...faster memory does almost nothing. At the very least, it improves perfromance by a miniscule percentage...ie...in value based computer building, is it correct to say then that I should almost not care about cas and timings and just got for the cheapest reliable ddr3 of 1333/1600 I can find?
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