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Problems with TWIN2X4096-6400C5C (ver6.1) on Asus P5Q (P45)


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Hello together


I’ve two identical Asus P5Q mainboards from the same serie and wanted to upgrade the systemmemory from 4 GB to 8 GB.


Until now each board was running with one 4 GB kit TWIN2X4096-6400C5C without any issues. I‘ve tried both kits on one board to test how it works with 8 GB and all slots occupied. Everything runs fine without any voltage adjustements. Memtest & Prime95 runs over night without errors, and all my applications and games worked without any problems. So i ordered 2 more of this kits. But this ones i can’t get to run stable.


I can hold the following :


The existing kits are :

TWIN2X4096-6400C5C, 5-5-5-18 1.80V ver4.3 (09451079, Week 45 2009)


The new kits are :

TWIN2X4096-6400C5C, 5-5-5-18 1.80V ver6.1 (10340498, Week 34 2010)


Both kits ver4.3 running together without issues on both mainboards. But the new kits ver6.1 won't. One board runs only with one kit, with two kits the system can‘t start (no beep, no bios post. The other board won't even run with one kit, the system (bios and windows) starts only with one module.


I’ve increased the voltages from DRam and NB step by step. With 1.9V DRam voltage the second board boots up, but in windows i get sporadically bluesreens with different errors (various .sys files from display- to networkdriver etc.) Sometimes i get graphic errors and the image freezes, the more load on the system, the faster it crashes (when playing games immediately). I tried voltages from DRam up to 2.1V and from NB up to 1.36V (system won’t start with more). But the result was allways the same. I can’t get the machine stable. With both kits inserted the bios won‘t post. The other board, which runs smooth with one kit (4 GB) has the same issues when i insert both kits (8 GB).


The only thing which helps is to decrease the memoryclock. The 'better' board runs with 4 sticks up to 720 MHz (with higher FSB and smaller multiplier or vice versa, makes no difference). As the result with higher FSB and overclocked CPU is the same, i don’t think the northbridge is limiting. On the less 'tolerant' board i was able to run 2 modules with 667 MHz. With 4 modules the system won’t start. I don't like to experiment more on. Each stick passed the Memtest with the printed specs on it. Mixed operation (using ver4.3 and ver6.1) i have not tried.


I think the different results with my two boards are due to normal tolerances of the components / manufacturing. Both systems are 100% identical (2x Q9650, 2x Corsair TX650W, 2 x Asus GTX-460). Everything from the same series with identical revision numbers (purchased together at the same time). Only the memory versions are different (ver4.3 / ver6.1). Can someone explain why ver4.3 runs fine with both kits together without any adjustments at the specified speed (800 MHz, 5-5-5-18, 1.80V) and ver6.1 make such problems ?


Greets Dominik.


P.S. Swap two kits ver6.1 to two kits ver4.3 !



Edit :


I’ve also testet 2 older kits :

TWIN2X4096-6400C5, 5-5-5-18 1.80V ver3.1 (08440525, Week 44 2008)

Running together (8 GB) without issues, without voltage adjustments.

Seems like the actually ver6.1 is not compatible with my boards.

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Thank you for your reply. I''ve seen you have the PC6400 DHX C4 quad-kit. Nice to hear it runs @1066 MHz (PC8500). What are your voltages ?


I think my ver6.1 sticks needs something which my boards can't deliver - i can only adjust the voltages, which doesn't help. And i don't like to decrease the clockrate... If i want ram which runs @ 667 MHz, i can buy some kits of them. There must be some different requirements between this chips (ver4.3 / ver6.1), although they have the exact same specifications (voltage, timings & subtimings).


Should i buy 4 Sticks 667 MHz (PC5300) to find out that they run only @533 MHz, or should i buy 1066 MHz (PC8500) ones and hope they will run @ 800 MHz ? Just kidding...


I'll try to return my ver6.1 to the shop and wait some time to get another version.


Greets Dominik.

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