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Flex Mode: Need Clarification

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October 28, 2010 10:10:28 PM

Hello,

I purchased this CORSAIR XMS3 6GB (3 x 2GB) CMX6GX3M3C1600C7 RAM with the intentions of building a i7 machine. I am now considering a i5 build to save some $$$. Being that this is tripple channel memory and i5 chipsets support dual channel, I want to understand how this will work in an i5 system?

1. Will all DIMMS run in single channel or will 2 be dual and one single or some other configuration alltogether?

2. Most importantly will this cause a noticable performance hit? I know the difference between dual and tripple in just a few % but what should I expect running this set of RAM on a i5 machine?

3. Will it just be best if I am building a i5 PC to return this and get the proper dual channel kit?

I Thank You in advanced, and I applogized if this has been discussed before, but the treads I have found and read did not answer my particular questions and had conflicting opinions about how Flex Mode works.
October 28, 2010 10:38:32 PM

If its easy to return I'd return it.

for best performance you need 2 or 4 chips with a socket 1156 board.

running 3 would result in single channel memory. you can only do dual channel with pairs this is why you need 3 or 6 for socket 1366 as its triple channel

if its hard to return.. you could just run 2 of the chips.. or try to find a single chip exactly matching your set and run 4.
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a b } Memory
October 29, 2010 3:25:45 AM

Clearly if you can return it, do it....

Why does everyone claim that you get single channel. Flex mode allows you to get most of the benefits of dual/tri channel with odd numbers of sticks. This has been a standard feature from Intel for quite a while.

Here ya go

I7 with 4 sticks(out of the 6 slots the board has) in triple channel mode. The other 2 sticks are in an AMD system that had bad memory.


I would test in my I5 system, but it is an itx system and as such only has 2 memory slots.

I honestly can recommend the I5(after all most if the I5's have much more aggressive turbo) for most applications.
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a b } Memory
October 29, 2010 3:41:24 AM

*sigh* Ok lets get a few things straight:

1. RAM speed had little performance impact with normal every day real world gaming,etc type load. RAM bandwidth matters in servers/HPCs.

2. More RAM is almost always better than less RAM. You will notice the extra 2GB of the 6GB kit over the 4GB kit if you do any RAM intensive stuff (ie. rendering, massive mult tasking,etc).

3. Yes. 2 will work in Dual Channel and one in single channel. The worst case would be all of them will run in Single Channel, but see point #1 & 2 above.

4. RAM speed only really makes a difference in bench runs for normal PCs.

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November 1, 2010 2:11:41 PM

Best answer selected by thechief73.
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