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Question about Dual Channel Setup, how BIOS handles RAM, etc

Last response: in Memory
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August 24, 2012 5:15:38 PM

Yesterday, I upgraded one of my computers with more RAM. The setup of my mobo was like this.

4 Slots

Slot 1 and 3 were white
Slot 2 and 4 were blue

Before the upgrade, I used to use 2 sticks of 2 GB each on slots 2 and 4. This is what the mobo manual suggested: if i only had 2 memory modules, it wanted me to use the same color slots. That's fine... I never stress-tested it or anything, but I absolutely never ran into any problems at all.

However, when i added in my new RAM yesterday, I simply put them in Slots 1 and 3. Then I rebooted, and my computer freaked the *** out. Gave me a message about overclocking or changing the voltage or something. BSOD's occured twice in Starcraft games, and one BSD occured right after i booted up Windows. I told BIOS to use default values, but that didn't seem to help either.

The RAM was the same exact model as the old RAM (bought off the same Newegg page)

Looking at my mobo manual, I saw this:

Channel A: Slots 1, 2
Channel B: Slots 3, 4

So I switched them up so that the old RAM occupied slots 3, 4 (same channel). The new RAM went into slots 1,2. After rebooting, setting BIOS to default values, my system appeared pretty stable.

I ran IntelBurnTest 3 times.

10 iterations of "Standard" - passed without a problem

5 iterations of "Very High" - passed without a problem

10 iterations of "Maximum" - Returned an error that said: "WARNING! Linpack binary stopped unexpectedly. This could be a result of missing executables, unstable system, or a soft ware bug. If you have UAC enabled, please try re-running the program with administrative privileges."

Afterwards, I played a game of Starcraft. It went smooth as silk.

Right now, I've left it to run Memtest86+ at home. I ran it about 20 minutes before i left the house, but at that point, there didn't seem to be any errors.

Should I be worried about my system's stability (because of the failed Maximum IntelBurnTest)? Is it important that the same RAM occupies the same "Channels" in a Dual Memory setup? Why should that even matter (since they should be the same RAM anyway... although they were bought about a year apart)?

Also, a slight aside, my mobo is reporting that my memory is running at DDR3-1333 (665 MHz for each stick). These are all sticks of DDR3-1600 (the packaging says so). Should I look into manually setting my voltages to clear up all problems? Maybe BIOS is just not setting this stuff up right? I'm less worried about this, though, cuz i hear the difference between 1333 and 1600 is neglible, although it is a bit annoying to have paid for 1600, and have gotten 1333 performance.



RAM is G.Skill Ripjaws DDR3-1600

Mobo is Gigabyte Z68P-DS3
a c 109 } Memory
August 24, 2012 5:49:56 PM

If memtest86+ runs for a few complete passes without a single error, I would think your ram setup is ok.

But, Ram is sold in kits for a reason.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards can be very sensitive to this.
That is why ram vendors will not support ram that is not bought in one kit.

1600 ram is really 1333 ram that can be overclocked to run at 1600
Sometimes, this needs a bit more voltage, particularly if you are using 4 sticks and not 2.
In this case, you might be more stable if you upped the ram voltage a notch. Never past 1.65v, or you can damage your cpu.

The motherboard has a harder time managing 4 sticks vs. two because there can be only one voltage setting for all 4 ram slots.

Also, some ram is not compatible. The ram vendor has a configurator. Your ram should show up as compatible with your motherboard.

If you run cpu-Z you can identify your ram sticks, and what voltage and speeds they are running at.

And, yes, the ram speed makes little difference in real app performance or FPS. Read this:
http://www.anandtech.com/show/4503/sandy-bridge-memory-...
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August 24, 2012 8:21:37 PM

is it safe to say that the general rule is: RAM from the same kit go into the same channel (e.g. Channel A in a dual channel config)?
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a c 109 } Memory
August 24, 2012 9:07:28 PM

joakcbasse said:
is it safe to say that the general rule is: RAM from the same kit go into the same channel (e.g. Channel A in a dual channel config)?


If the ram is identical, it is a moot point.
The rule is to put equal gb of ram on each channel.
If you do not, the matching gb will run in dual channel mode, while the remaining will operate in single channel mode.
Not really a big thing for performance though.
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August 24, 2012 9:19:18 PM

geofelt said:
If the ram is identical, it is a moot point.
The rule is to put equal gb of ram on each channel.
If you do not, the matching gb will run in dual channel mode, while the remaining will operate in single channel mode.
Not really a big thing for performance though.


well, i guess i have a case for it not being a moot point, since i had this experience.

hopefully, it serves as a lesson learned to anyone reading this thread....
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