Asus P5Q Pro Turbo and TWIN2X4096-6400C5C

[ajmiles]

Hi,

 

I bought two of these 4GB kits with a view to using 8GB, but on trying it I got nothing but failures while installing Vista. In an attempt to get it working I went back to just 1 stick in slot A and this works fine.

 

I've now tried adding 1 extra stick into slot C (2 * 2GB now) and there's massive system instability, and Vista Memtest failures almost instantly. My combination of failures so far is:

 

Slot C,

Slot A and C,

Slot B and D,

Slot A, B, C and D

 

Since I have two sets of matched pairs, I've tried both pairs independently of each other and both fail in some combination of slots, so if the memory is bad, its at least one stick in both pairs. This memory is listed as compatible, and the motherboard is picking it up at 5-5-5-18 and 1.8V correctly.

 

I'll be able to try more combinations of RAM / slots / memtest after work tomorrow, I'm just hoping for some suggestions before then so I can get straight to it :).

 

Many thanks,

 

Adam

 

EDIT: Just worth mentioning that when I say it's compatible, the QVL says it's compatible with the 6400C5 (but not C5C), but I did read in another thread that the only difference is the heatspreader, so it counts as being compatible. Right?

[RAM GUY]

We do not officially support mixing memory even if you have two set that are the same part number and version we would normally suggest the next lower speed grade. But in a nut shell XM2X-6400C5 and XM2S-6400C5C are the same basic part.

With 4 modules I would suggest setting the memory frequency at DDR667 and set the memory Voltage to 2.0 Volts and set the NB/MCH/SPP Voltage to +.2 Volts as well and test the system with http://www.memtest.org. In addition, with some MB's (Mostly ASUS) you have to disable legacy USB in the bios when running any memory test.

[ajmiles]

My problem has nothing to do with mixing memory though since I can't even get 2 sticks (2x2GB) working at Auto settings. My only successful combination so far is 1 stick in 1 slot, 2GB.

 

I can see from the serial numbers which 2 sticks came with each other so whenever I try to run 2x2GB I'm always using the matched pairs. I've tried both pairs independently of each other in both slots A/C and B/D, no combination of 2 matched sticks work in either the yellow or the black slots. Forget 8GB configurations for now, that's just a pipe dream until I can get 2x2 working.

 

The RAM is on the QVL so should work in at least a 2x2GB configuration without lowering the speed to 667 or upping voltages otherwise I fail to see why it was put on the QVL.

[RAM GUY]

I cannot speak for the QVL List from the MB maker as we have nothing to do with that. Only that when mixing two twin sets the next lower speed grade would be suggested. Now that being said does not mean it will not work only that we cannot promise something we do not test..

 

If I understand your last post you cannot even get two modules to run in D/C is that correct and did I miss understand???

[ajmiles]

That's correct, no dual channel with either matched pair, in either slots A/C or B/D. Unless you can suggest anything else for me to try I guess the thing to do would be to verify all 4 sticks individually (1 stick at a time, 2GB, single channel) and then try and figure out whether its only certain slots on the motherboard that exhibit the memory errors.

 

Are sticks of RAM put under any greater load in dual channel mode that would explain why I can run in single channel mode but not dual?

[RAM GUY]

That would suggest a problem with the CPU, either the memory controller is failing or it is not getting enough stable power.