P5N64 WS Pro Memory slot 1

[mbeifuss]

I've been running 8GB GSkill Ripjaws F3-12800CL9D-8GBRL on a ASUS P5N64 WS Pro and recently decided to move up to 16GB and I got 8GB GSkill RipjawX F312800CL9D-8GBXL. When I installed the new sticks the computer wouldn't boot. I got a second kit thinking that was the problem and that didn't help. I got it to boot by upping the NB voltage and the memory voltage to 1.66V. However if I populate all 4 slots with the 'X' version the computer won't pass memtest 4.20 consistently failing on test #5. If I put a stick of the Ripjaws (not 'X') into slot 1 (closest to the cpu) then all the computer passes memtest. Any idea what is the difference between the Ripjaws and RipjawsX that would account for this? Can I mix Ripjaws (slot 1 and 3) and RipjawsX (slot 2 and 4)?

Thanks,

[Tradesman]

A) the sets (even of the same model) might not be compatible, B) may be a bad stick among them (can run memtest on each stick individually to see if all good) C) you want the FSB at 1600 for the sticks (which also may mean needing a 3rd party CPU cooler), D) NB may be to low E) vCore may be to low for the OC F) BIOS may be outdated G) DRAM voltage may be to low .... a few thoughts anyway

[mbeifuss]

I am running the memory unlinked at 1600 MHz (CPU is at 1833 MHz FSB (3.9GHz) 1.296V with droop) with a Tuniq Tower 120 Extreme (temps are low 50s C under prime95). I tested each stick in and they all test okay until I put 4 sticks in then all of the RipjawX's in slot 1 cause a memory failure. NB voltage is set to the max safe value as determined by the mobo (higher settings are in yellow). BIOS is the latest (0802) and the DRAM voltage is set to 1.68V (highest the mobo calls safe, 1.70V is in yellow). The memory timings are manually set to 9,9,9,24,2T,auto... which should be the default settings.

There just seems to be something different between the Ripjaws and RipjawXs when in slot 1 of the mobo.

Thanks,

[Tradesman]

Given it's socket 775, I'd guess that haven't updated the BIOS around the X version, which was designed for next gen CPUs and around the P67, Z68 chipsets, I'd try the regular Jaws in slot 1 and if need be raise the DRAM voltage a bit more, can even take the NB slightly into the the yellow (unless going 24/7....another option would be try 1333 at 8-8-8-24 which will be near same as native 1600