Asus P7P55D Deluxe and CMX8GX3M4A1600C9 - Only 4gb usable

Hi all,

I recently upgraded my machine to a Lynnfield i7-860, running on an Asus P7P55D Deluxe board. For memory, I chose the Corsair CMX8GX3M4A1600C9 8gb memory kit.

The problem I have is that the BIOS and Windows both only 'see' 4gb. Windows itself (Win7 x64) will see all 8gb, but classifies 4gb of it as 'hardware reserved'.

CPUID also shows 8gb of physical ram in the machine.

I had a look at some other threads in this forum and saw a potential issue with 1600mhz ram and Asus motherboards, however I noticed when I boot up, the motherboard has been setting the ram to run at 1333mhz by default.

I have tried changing the settings in the BIOS to try the XMP profile (which runs the ram at 1600mhz, 1.65v and 1.15v on the controller) - still only 4gb.

I then tried Auto settings with the ram speed at both 1333mhz and 1067mhz - but still only 4gb recognised and usuable.

The reason I'm posting here is, regrettably, I didn't see this problem immediately after upgrading as I've been busy with other things. I had naturally assumed all 8gb was available and it wasn't until I was looking in Task Manager one day and noticed the missing ram! This delay has meant my retailer will refuse to refund or exchange the ram for a different Corsair pack, so I can't easily tell if it just happens to be a fault with the memory.

Can anyone suggest anything else I can try? I really don't know at the moment if this is a problem with the motherboard or the ram, and I don't know how else to proceed :(

Thanks RAM GUY,

I've identified DIMM #3 as being at fault in some way. The system wouldn't boot using AUTO settings with this dimm, so I gave MemOK a try. It eventually managed to POST, showing the dimm running at DDR3-800 to achieve this.

Is this enough evidence to start an RMA, or are there any more tests I should run first? Also, would the RMA be to Corsair directly, or to the retailer I got the ram from?

Look forward to hearing your advice!