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I was using a 2GB DDR3 ram stick on my last Computer, I got a new motherboard which had an offer for 4GB so I took it, got home and discovered it was actually 8 GB DDR3 RAM, two identical 4GB sticks. Pretty cool. :P

Anyway, The motherboard has four slots, two blue and two black. They are arranged like this:

Blue | Black | Blue | Black

I have placed the two 4 GB sticks in the blue slots, and the spare 2GB i had in a black slot. It's probably overkill, but might as well use it I figured.

Is this the correct way to arrange them? Would the 2GB hurt performance, with how channels work?


edit - motherboard is a ASUS M5A 78L-M USB3

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This is probably right, but is motherboard dependent - can you edit and add your motherboard make and model. – Paul May 22 '12 at 5:56
what mainboard do you have exactly? "black" and "blue" is not very helpful in this situation. did you read the manual of your mainboard? there are usually hints about how to mix the bricks. – akira May 22 '12 at 5:57
It is an ASUS M5A 78L-M USB3 – jiio May 22 '12 at 6:00

In general, two slots of the same colour are on different channels, and the way you've put it seems to be logical. Assuming the system supports a mix of dual channel and non dual channel ram, the two blue sticks are working in dual channel mode, and the stick in the black slot isn't. Otherwise they're all running as seperate channels (which dosen't cause THAT much of a performance hit).

You shouldn't have any issues with the layout. You can get information on whether you're running in dual channel mode, and what variation of it with cpu-z

enter image description here

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Actually, while you'd think that was the case (same color = same channel), it seems there are two different interpretations which different mobo makers subscribe to. – Mahmoud Al-Qudsi May 22 '12 at 6:43
My motherboard manual, and Intel's page, indicate that the same colour indicates a pair (group) of slots, not a channel. A colour has one of each channel. So if both blue are used, one stick will be in each channel - dual channel. And I've tested with my motherboard, as long as one stick is in each channel (even if one's in blue, DIMM 1, and one in black, DIMM 4), it will use dual channel mode. That is contrary to the manual, and may vary by motherboard. CPU-Z is definitely one way to confirm. – Bob May 22 '12 at 6:43
hmm, appears my understanding of it was wrong, and the my practical application was right. Editing the answer to reflect that – Journeyman Geek May 22 '12 at 6:50

Just to clarify, seen as tho there is so much confusing evidence online around this subject:

Dual channel boards have two channels, duh, Channel A and Channel B. Various mainboard manufacturers colour their slots, but if like mine yours is all the same colour, they are usually laid out like this


So, if you have matched RAM sticks, you always want to place them on different channels, so if 'x' is a stick, and '.' is empty spot:

[x.][x.] or [.x][.x] Whichever best fits your CPU HSF

Remember that you are splitting the bandwidth bottleneck between two controllers.

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From the manual, it states that pairs should be in the like coloured slots.

So the way you have it populated is correct. A pair in either the blue or the black slots, and they will be accessed in dual-channel mode. The remaining stick in either of the remaining slots to be accessed in single-channel mode.

The 2GB will not hurt performance, specifically, but memory stored on them cannot be accessed as fast as it can be from the pair of 4GB sticks. However, having the additional memory available for caching will very likely negate any performance overhead from accessing its contents in single channel mode.

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The 2GB stick, being older, probably is harming performance. The memory controller has to operate at the slowest speed and timings supported by any of the memory modules installed into slots on that channel.

Look at clock speed (the number in DDR3-xxxx, such as 1066, 1333, 1600, high numbers are good) and CAS latency (CL=n, low numbers are better).

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