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Another D975XBX2 and 6400C4 question


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I moved from an Asus P5W DH to Intel D975XBX2 due to a spec build

issue for an add on card I have to use in my video work.


When I rebuilt, I transfered my E6600 and the 2 pairs of TWIN2X2048-6400C4

to the Intel MB. This was back in September 2007. I was able to run

directly at 4-4-4-12 800MHz with the Vddmem set to 2.08v.


In the past two weeks I have been experiencing reboots for IRQL_NOT_LESS_OR_EQUAL in WinXP. This was only occuring when I was heavily processing video or audio (using all the RAM up).


I know the 4GB doesn't buy me much on this setup, but I have the /3gb switch in the boot.ini and the little extra I get seems to help quite a bit.


So, got memtest86+ v1.7 out and started in on it.


First, ran each stick one at a time in slot A0. This was at 4-4-4-12 800MHz

with Vddmem at 2.08v. I found 1 stick which gave errors on test #6, and yes, legacy USB is disabled. I moved to 5-5-5-18, but left the clock and supply alone. This one stick failed the same at 5-5-5-18 with Vddmem at

2.08v and clock at 800MHz, but seems to be fine at 667MHz (this is in A0 by



I ran the passing units in as dual channel pairs. One seemed to have an issue running in dual channel at 800MHz, but ran OK at 667MHz. I swapped out the unit I thought caused the issue (in B0, left A0 in) and the new pair ran fine at 800MHz.


So, two things:

1. I know that we can't run (4) 1024 sticks at 800MHz, but I was doing

that for months before this started up. Would I be able to run a pair

of 2GB sticks at 800MHz with this MCH?


2. Shouldn't any one stick alone in A0 (asynch mode) be able to pass at

5-5-5-18 800MHz Vddmem=2.08v? If not, and an RMA is in order,

since this is a pair (TWIN2X2048-6400C4) shouldn't I send the pair

in to you instead of just the one stick?


For now, I am just going to leave the pair in question out of the machine.




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With 4 modules the 975 chipset will be limited to DDR667, however all modules should have no problem running at DDR800 at 2.08 volts with timings of 4-4-4-12. If you have a module that will not run at its advertised spec then we would want to get the pair replaced. Please use the On Line RMA Request Form and we will be happy to replace them.
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Thanks, Ramguy,


I will process an RMA for the pair. However, I asked a rather pointed

question. In dual channel setup, the 6400C4 should be able to run

at DDR2 800MHz with one set of TWIN2X2048-6400C4 in A0 and B0.

Am I wrong in stating this?


I have moved Vddmem up to 2.12v, moved

the MCH supply up and back, and I have not been able to obtain stability

with DDR2 800MHz with either 4-4-4-12 or 5-5-5-18 timing. Running at

667MHz seems very stable with most pair combinations.


All 4 sticks are serialized from 100522432 to 100522435.


Eventually, I want to bring this E6600 (7x343MHz) to a 1:1 with

the ram speed.




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That's fine, but the last question I asked was about 2 modules

running at 800MHZ DDR2. It seems that doing that is on the

edge on this board too. Sometimes OK, sometimes not. 2 out

of 10 full passes of memtest86 on the 2GB failed on test #5 right

at the address boundry between modules. Swapping the modules

slot location helped. However, I question just how close to the

edge this board is running at 800MHz.


I figured I could get a 1:1 setup and then bring up the FSB till

the speed becomes an issue.




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