Corsair 6gb 1600mhz only showing 2gb

May 15, 2010 at 15:05:07
Specs: WIN 7 Pro x64, iCore 7 oc 3.40, Corsair Dominator TR3X6G1600C8D
ok after a few months of Windows 7 upgrade from Vista, my ram is not showing up as 2gb.

Asus p6t
Cooler Master ATCS 840
Corsair HX1000W PSU
Noctua heatsink
iCore 7 920 OC 3.40ghz
Corsair Dominator TR3X6G1600C8D 6GB 2x2x2

Now Memtest86+ will run fine on each module installed individually. Works with slots (orange) 2,4 and shows 4GB in Win 7, but when the third module is installed it shoots back only 2GB installed in Win 7.

I'm assuming that potentially the third ram slot on my Motherboard is defective? Is this common? The ram passes the stress tests individually.

Reason I noticed this was that I kept BSOD'ing when playing games to a certain point or doing intensive file scanning for duplications etc...

Any suggestions short of spending 300$ on a new MB?


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May 16, 2010 at 16:13:06
You have a 64bit system?
Which version of windows 7 do you have?

Try checking each slot by itself and see if your comp reads the right amount and try plugging that last stick into a slot that you know is working. As well as making sure all sticks are securely in place.

Also, what does your BIOS read for your ram?

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May 17, 2010 at 11:57:42
I'm assuming you're running Windows 7 64 bit as you list in the blue bar of your first post.

"iCore 7 920 OC 3.40ghz"

The Asus P6T mboard apparently supports this cpu, BUT you are overclocking this cpu considerably.

Supported cpus
Core i7 920(2.66G,L2:4x256KB,L3:8M, rev.D0,130W)

There is NO guarantee that your ram will be recognized properly, depending on what overclocking settings you used.
It is easy to choose inappropriate overclocking settings, unless you find specific info on a web site that speciallizes in overclocking info for what settings are appropriate and stable for your EXACT mboard model and the ram you're using. Also, what is stable may vary considerably depending on which cards you have installed in slots, e.g. which video card, and how it/they handle their bus speed being overclocked.
If you're not sure whether you're choosing appropriate stable settings, BACK OFF on the overclocking settings, or don't overclock at all, until you get the ram working properly.
DO NOT Overclock beyond the point where the ram is no longer recognized properly !


- this ram set has a 8-8-8-24-2T ram timing rating.
It will work fine if the ram timing numbers in the bios are HIGHER (slower), but there's no guarantee the ram will run fine if any of those numbers are LOWER (faster).

- this ram set is rated to run at 1.65v - it may NOT run properly at a lower voltage, and you should NEVER run it at a higher voltage, because........
Page 36 of the P6T mboard manual.

"According to Intel CPU spec, DIMMs with voltage requirement over 1.65V may damage the cpu permanently. "

The memory controller is built into the cpu, not the mboard main chipset.

For non-overclocked systems, or in any case...

Some ram manufacturer's modules do not strictly adhere to the JEDEC standards that most mboards bioses use to determine ram settings.
In that case, the ram settings in the bios Setup that the bios has automatically chosen may not be correct.
Check the ram settings in your bios - the ram voltage, and the ram timing numbers - those should be the same as for the specs for the modules themselves. Often the ram voltage and timing numbers are printed on the label on the modules.

If the voltage setting or timings settings in the bios are different from the specs for the ram, change them in the bios. The timing numbers must be as close as you can get to the same, or slower timings (higher numbers = slower) - you won't notice the difference the slower settings make.

Defective ram slots or their associated circuits being defective are extremely rare,
UNLESS you damaged it/them when you DID NOT remove the AC power source to the power supply at ALL times when you were plugging in or unplugging the ram.
The ATX mboard is always powered in some places, including some of the contacts in the ram slots, by the ATX power supply as long as the power supply is receiving live AC power, even when the computer is not running.

Did you remove the AC to the power supply at all times when you were fiddling with the ram inside the case?

"Corsair Dominator TR3X6G1600C8D 6GB 2x2x2"

Corsair lists the TR3X6G1600C8D 6GB 3 module set for the Asus P6T, so that should work - I have no idea where you're getting the 2x2x2 from.

TR3X6G1600C8D DDR3-1600 (Dominator-12800C8*XMP*3CH) 6GB Kit (3 x 2GB) 1.65v 8-8-8-24-2T

Asus lists the TR3X6G1600C8D set in their tested memory list

Qualified Memory support list - the newest one

For: TR3X6G1600C8D DR3-1600 (Dominator-12800C8*XMP*3CH) 6GB Kit

A* - Supports 2 modules inserted into A1 and B1 as one pair of a dual channel configuration
B* - Supports 3 modules inserted into the orange slots A1, B1, C1 as one set of a triple channel memory configuration
C* - Supports 4 modules inserted into the orange slots A1, B1, C1, and the black slot A2 as one set of a triple channel memory configuration
D* - 6 modules - NOT supported for the modules in this set

- it is recommended to install memory modules from (into) the orange slots for better overclocking capability
- the default DIMM frequency depends on (the information found on) it's Serial Presence Detect (SPD) which is the standard way of accessing information from a memory module. Under the default state, some memory modules for overclocking may operate at a lower frequency than the vendor-marked value.

My note - in other words, if you overclock, the ram may not be able to run at it's rated speed, or, possibly, not all of the ram will be able to run at it's rated speed.

"Now Memtest86+ will run fine on each module installed individually."

It doesn't say in the mboard manual whether a single module will work in any ram slot. Since all 3 modules test fine individually in whatever ram slots you tested them in, there's nothing wrong with the modules.
You SHOULD be installing all 3 modules ONLY in the ORANGE ram slots in order for all to run in triple channel mode. If you install ANY of the 3 modules in other ram slots, there's no guarantee that the total amount will be recognized properly.
If you ARE plugging all 3 modules into the orange ram slots, and then only 2gb total is recognized, then, yes, it could be whatever third ram slot you're plugging into or it's associated circuits have been damaged, if you're NOT overclocking.
If NONE of the three ram modules are recognized individually in whatever third ram slot you're talking of, that may or may not be significant.

Page 36 of the P6T mboard manual.

Due to Intel spec defintion, X.M.P. DIMMs and DDR3-1600 are supported for one DIMM channel only.
(My note - that means you cannot install two sets of 3 modules.)
According to Intel CPU spec, DIMMs with voltage requirement over 1.65V may damage the cpu permanently.

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