I have a very strange problem with my ASUS P8Z77 V Pro where it now see's half the memory installed.
I turned my computer on a couple of days ago and the POST said Overclock failed, press F1 to set BIOS... What's weird about that was that my computer wasn't overclocked. I only set the RAM to run at 1600MHz in the BIOS. I built this PC in mid-July and it's been running perfectly fine since then, with all of the RAM usable.
I've tried all of the troubleshooting steps I know since the problem began:
1) I reset the BIOS to the optimized defaults but it still only saw 8 GB of RAM (still dual channel tho)
2) I reseated all of the RAM sticks and tried different combinations. Usually I have 1 of each F3-12800CL9-4GBXL on slot 1 of each channel and 1 of each GSkill F3-17000CL11-4GBXL in slot 2 of each channel. I flipped these but the problem continued. I also tried putting all F3-17000CL11-4GBXL on channel 1 and all 12800CL9-4GBXL on channel 2 and vice-versa but the same thing happened.
3) I cleared the BIOS by unplugging the PC and pulling the battery and letting the computer sit for 15 minutes but when I booted it still only saw 8 GB of RAM
4) I upgraded the BIOS to 0906 to 1610 to see if it would fix the problem but it didn't. I also reset it to the optimized defaults and pulled the battery for 15 minutes with no positive results.
5) I tried each dual channel kit by itself but both of them work fine. Each got through at least 3 passes of Memtest86 4.0a with out any errors. But if I tried will all sticks in the computer MemTest would still only see 8GB of RAM. I also tried booting Ubuntu 12.04 and it also sees only 8GB of RAM.
6) What makes this even weirder is when I boot into Windows, Computer properties says 8GB of RAM (7.46GB usable). I am guessing somehow the iGPU got activated but GPUz doesn't see it and I can't find any options for it under the BIOS. Even under the GPU configuration screen, the only options are Auto, PCIE and PCI. I get no video if I remove my Radeon and plug directly into the motherboard DVI port.
7) CPUz also reports all of the RAM and it can see each stick of RAM under the SPD tab. Windows can't tho and I don't know why. I checked under the DRAM timing controls and both DIMMs on each channel are enabled. Also, the SPD View utility in the BIOS can see all of the RAM sticks.
8) Back in Windows, I even tried the msconfig → boot → advanced options → Use Maximum Memory but that did nothing.
At this point, I have no idea what's wrong with my computer. I am going to try testing each ram stick individually but that will take a while. Unfortunately I don't have another DDR3 computer at the moment to test the RAM on.
If anyone has encountered this problem before, please let me know what other steps I can take to fix it.
CPU - Core i5 3570K
MB - ASUS P8Z77 V Pro
RAM - 16 GB (Now only 8GB usable) running at 1600MHz
-- 2x GSkill F3-12800CL9-4GBXL
-- 2x GSkill F3-17000CL11-4GBXL
Video - XFX Radeon HD 5770
OS - Windows 7 Enterprise 64bit