Asus P8P67 problem does not detect all memory

[4ghz]

I have 8 GB (4x2GB sticks) installed but BIOS only detect 4GB installed rather than 8GB I expected. I have reseated all 4 of them, I have rearrainged them, BIOS seems to only detect 2 sticks. If I run CPU-Z it does show all 4 sticks for 8GB total. Windows and BIOS however report only 4GB.

Windows 7 64-bit (yes, 64 bits I checked it)
Intel 2700k
Asus P8P67 Pro (uses UEFI rather than legacy BIOS)

Either one of the slot is bad or there's a setting in BIOS that may be inadverantly disabling one set of slots. Anyway to check on that?

 

[micropage7]

have you tried to reset your bios too?

 

[Steve-007UK]

Don't some mobo's have a memory mapping option in bios that needs to be tunred on or off so all ram is seen? Sure i read about that a few times with asus boards.

 

[Aquinus]

Did you try reseating your CPU? Don't over-tighten the cooler either as too might force might prevent some pins from making good contact. Can you get the machine to start up with DIMMs in just one channel or the other?

 

[4ghz]

Tried reseating CPU, tried reseating RAM, tried RAM in another computer, tried RAM from another computer in this one. Last week, it started failing even more, detecting only 1 stick, then it won't boot anymore, stopping at error 55 (RAM not installed)

I just got a replacement mobo in today, installed, setup, and all 8GB was detected on the first try. So.... my older mobo was a lemon whose problem wasn't discovered for a couple years. :/ Probably bad trace or cracked solder or something but mobo repair isn't my forte. Worse, the motherboard is just a few months out of warranty.