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Hi, I successfully installed a genuine OEM copy of Windows 7 Pro x64 on my P5KC system. It was running 2gig 800mHz DDR2 ********. So, wanting to upgrade to DDR3, I bought 2 x 4gig Corsair vengeance DDR3 1600mHz for my P5KC (part number CMZ8GX3M2A1600C9B).


Fact: prior to installing Windows 7 Pro x64, I was running XP Pro SP3 32-bit, I installed the new RAM to see if there would be a compatibility issue. There was not! The BIOS recognised the new RAM and POSTed properly.


Like many people, I had "issues" installing the new operating system, and so, as per the advice I have read on many forums, I stripped the PC back to basics (which i will note at the end of this post), re-installed the ******** RAM, and presto! Windows 7 successfully installed. After all drivers were updated, the PC was running very well - happy camper! I decided to install the DDR3 Corsair memory.


PROBLEM: With 8gig of Corsair DDR3 memory installed, the PC will not boot at all - nothing! But it will boot with the ******** DDR2.


QUESTION: If it's not a memory/mobo compatibility issue, what could be the problem?


The PK5C does support both DDR2 and DDR3. I understand that 1333 is the highest supported speed.


What I am trying to fathom is why does the DDR3 RAM work when XP Pro x32 is installed, but not when Windows 7 Pro x64 is installed?

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I have the same board and memory (see spec) and the problem is this board (natively only supports up to 1066 memory "p35 chipset" 1333 OC with some memory.....).


also when booting it reads the SPD and sets the voltage @ 1.5v (which on this board is way to low (mine is @ 1.8v, max rating is 2v) and mis-reads the timings very badly I use 8-8-8-22 @1200Mhz Dual (so 600Mhz each).


I had to force it to safe boot so you get the "Overclock failed!" message.


1. Turn on with ddr2 in.

2. restore defaults in bios

3. then use the jumper to reset Bios.

4. change over memory to ddr3

5. boot and let it just sit with fans running for a min(aprox) (nothing on screen and fans will be running on default max)

6. "press and hold" the power button until the fans stop, then quickly press the power button again the PC should power up fans @ max, then the fans should slow to medium speed and boot to Bios failsafe, where you should be able to setup your ram timings & voltage, etc.... and save and reboot. (do not load an old save OC profile!)


It may take you quite a few starts to get to bios fallback (it did for me!)


NB. ASUS only state support for up to 4Gb of ddr3 because of issues supporting more on this chipset. which is why you need more voltage and to slow it down.


NB. on some cold starts you may have to reforce your way back to bios and then just save the settings again and it will work? not sure why as it happens very randomly for me (but only from cold/never on a reboot).....


edit:also if you are OverClocking you may need to push up the NorthBridge Voltage

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  • Corsair Employees
I am sorry but this MB will not support our Vengeance modules, the Chipset that is used on this MB will only support memory modules made with memory IC's that are 256M By 8 in configuration and we use 512M X 8 memory IC's on most if not all of our current production DDR3 memory.
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  • 3 weeks later...
I RMA'd the DIMMs back to Taiwan, and a just yesterday, I received a delivery from Corsair. The had replaced the DIMMs with a new set. Filled with hope, I installed the new DIMMs, held my breath and hit the Power button. Blank screen - zip - zero - zilch! The new DIMM's made no difference. Again, I tried using a single DIMM in each slot, no joy. I tried CLRTC (as was suggested on another site), but this didn't solve a thing. So, I put the old DDR2 DIMMs back and find myself here again. I am thinking that I will write off these DDR3 DIMMs and source 4 x 2G Kingston HyperX DIMMs.
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