[64 bit] Memory not being fully detected

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http://ubuntuforums.org – I recently installed Ubuntu 11.10 64-bit. I also just got two sticks of 2G DDR 400Mhz ECC Reg. Ram for my computer (It requires ECC Reg for anything a Gig and Up) for a total of 6 Gigs. The motherboard is an H8DCE, if that helps. Anyway, I installed the ram yesterday, and at first it would detect it all in the bios, but not in Ubuntu (Which only detected 4.8). Then I switched the new ram onto one processor on alternating DIMM slots, and it detected correctly (at 5.8 Gigs). But when I booted up today, it wasn't detecting it correctly in the bios or in Ubuntu, as both were getting 4.8 Gigs. (Hardware)