Windows 7: ASUS P5KC - 8gig RAM - Won't boot Win7 Pro x64

Hi, I successfully installed a genuine OEM copy of Windows 7 Pro x64 on my P5KC system. It was running 2gig 800mHz DDR2 Kingston KHXxxxxxxxx. 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 Kingston 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 Kingston DDR2.

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

SYSTEM:
CPU: Intel E8500 @ 3.16gHz
BIOS: 1203 (latest version)
DVD: LG 4166B
HDD: 1 x 250G WD Caviar
RAM: 2Gig DDR2 800mHz Kingston KHXxxxxxxx
GPU: Gainward HD3870 512MB
O/S: Originally XP Pro SP3 32-bit --> clean install upgrade to Windows 7 Pro x64

Did you look over the board specifications before ordering the new DDR3 memory? With the DDR2 Kingston memory all went well since the board supports the older memory and may not run with DDR3 unless it supports both as seen with Socket AM2+ boards that have both DDR2 and DDR3 memory slots.

The specifications would suggest this was the case. http://www.asus.com/Motherboards/Int...specifications

The specifications show DDR3 1333 as the fastest DDR3 speed supported. To continue running the faster 1600mhz memory you would need to back the memory clock down to the 1333 speed. That would be the same for installing DDR3 1800 here on a board that runs DDR3 1600 memory.

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?

One notion would be the 32bit XP is simply mapping out over 4.gb of the new memory while the 64bit 7 is trying to load data into memory that is incompatible. Besides two different versions of Windows you are going from the 32bit kernel to the 64bit.

In addition to that the hardware profiling is much different being updated in 7 over what XP was based on. Windows 7 is a bit more intelligent OS as well for seeing things like hardware protection.

Hi,
asus p5kc supports 4gb of ddr3 only that is the limitation.

Under Memory:

I had to go to the Canadien site since the global site was sitting there for an hour spinning in circles but the specs are the same. http://ca.asus.com/en/Motherboards/I...specifications

Hi,
as the site you mentioned had this content
2 x DIMM, max. 4GB, DDR3 1333*/1066 / 800 MHz, non-ECC, un-buffered memory, dual-channel memory architecture
4 x DIMM, max. 8GB, DDR2 1066*/800 / 667 MHz, non-ECC, un-buffered memory
Dual channel memory architecture
* The chipset officially supports the memory frequency up to DDR3 1066MHz/DDR2 800. Due to the tuning by ASUS exclusive technology, this motherboard natively supports up to DDR3 1333/DDR2 1066MHz. Please refer to www.asus.com or user manual for Memory QVL

If you fo through that * commented line you can use 1333 mhz ram ddr3 which is clear.

This might help.

Front Side Bus 1333 / 1066 / 800 MHz
Memory 2 x DIMM, max. 4GB, DDR3 1333*/1066 / 800 MHz, non-ECC, un-buffered memory, dual-channel memory architecture
4 x DIMM, max. 8GB, DDR2 1066*/800 / 667 MHz,