First post. Please be gentle?
Here's the setup:
* Intel i7-920, retail with the included heatsink / fan
* Asus P6T Deluxe (not the version 2) motherboard
* Corsair AX850 power supply
* Video Card: nVidia GeForce GT 220 (by Asus) with like 1GB on it or something. (I'm not a video card guy...)
I had 3 sticks of OCZ DDR3 PC3-12800 2GB RAM. About a week or two ago, I noticed that the system was only reporting 4GB of RAM rather than 6GB. I figured the RAM was bad. I used that as an excuse to upgrade!
I purchased 3 sticks of Corsair 1333MHz DDR3 4GB RAM. It now reports 8GB of RAM, rather than 12GB. I swapped sticks around. It seems like it only reports the capacity of whatever is in slot A1 & B1 on the motherboard. (Triple channel configuration is to use A1, B1, and C1)
Asus was nice enough to RMA the (under-warranty) board. The new board is having the same symptoms, making me think it isn't the board.
In all cases, memtest86+ reports that the SPD bus reports that all three slots are accurately occupied. In other words, if there are three 2GB sticks in slots A1, B1, and C1, then that's what is reported. Yet, in all cases, the total amount of memory reported by memtest86+ and the BIOS is always the sum of the first two channels.
Does all that make sense?
So, I've changed memory, yet the symptoms are the same. I've changed motherboards, yet the symptoms are the same. I've done this with my extra SATA controller pulled, yet the symptoms are the same. I've done this without any SATA drives connected, yet the symptoms are the same. I've even changed cases to get different USB, Firewire, and HD Audio ports, yet the symptoms are the same! The only thing I haven't swapped is the power supply, CPU, and video card?
Since the memory controller is on the CPU, would that be it?
Regarding overclocking: I'm basically not doing it. Somewhere between 6-10 months ago, I did some testing at higher speeds for a few hours. I had an experienced over-clocker with me to help me keep an eye on things (temp's, voltages, etc). At no point did things get out of spec to the point where the system shut itself down. Nor did my "expert" ever get nervous. That was for about 2-3 hours, many months ago. I really don't feel like it would be related. I include it for the sake of completeness.
I did some Google searches, and searched the archives here. This is the only thing I've found that seems similar to what I'm experiencing:
Obviously, it is a different board, but the symptoms are similar.
Anyone have any ideas?