16GB of RAM installed, ~12GB useable

memory

Specs:

  • Motherboard: Crosshair V Formula-Z
  • CPU: AMD FX-8150
  • Memory: G.SKILL F3-2400C10Q-16GTX Trident X 16GB 4X4GB DDR3-2400 CL10 240PIN 1.65V Quad Chann *IR-$10*
  • OS: Windows 8 Pro x64 (It did this with Windows 7 x64 Home Premium too, but I though it was because of the RAM limit)
  • Graphics Card: EVGA GTX-680

Wath the task manager says:

  • Memory: 16.0 GB DDR3
  • Speed: 1600 MHz
  • Form factor: DIMM
  • Hardware reserved: 4.1 GB
  • Committed: 2.7/11.9 GB

What my motherboard says:

  • Memory: 12*** MB
  • Speed: DDR-1600 (Tried 1333 too)
  • Says that the 4 DIMM are filled with 4GB RAM each

What CPU-Z says:

  • Size: 16*** MB
  • Channels #: Dual
  • NB Frequency: 220*.* MHz
  • DRAM Frequency: 802.7 MHz
  • FSB:DRAM: 1:4
  • CAS# Latency (CL): 9.0 clocks
  • RAS# to CAS# Delay (tRCD): 9 clocks
  • RAS# Precharge (tRP): 9 clocks
  • Cycle Time (tRAS): 24 clocks
  • Bank Cycle Time (tRC): 46 clocks
  • It also detects all 4 slots of RAM correctly with the correct informations

Memtest86+

  • Reported only 12 GB of RAM

What I tried:

  • Disabling the "Maximum memory" option in msconfig (It was disabled by default)
  • Enabling the "Memory remapping" option in the UEFI/BIOS settings (It was on by default)
  • Updating my BIOS firmware

What would cause such amount of RAM to be Hardware reserved?

Best Answer

This is almost always caused by an improperly seated CPU or a damaged CPU socket. Another possibility is a damaged or contaminated RAM socket. The giveaway is that precisely one stick of memory is missing.

To confirm this diagnosis, try removing both sticks from one channel. Then try removing both sticks from the other channel. If one channel recognizes the full memory and the other doesn't, check the other set of RAM in the bad channel to confirm that it is the channel and not the RAM sticks.

If you confirm the diagnosis, check the RAM sockets on the problem channel carefully. Make sure no dirt or other contamination is evident in the RAM sockets.

If that doesn't resolve the problem, take the heat sink off the CPU and then remove the CPU from the socket. Inspect the CPU's bottom for cleanliness. Check the socket for any damaged pins. By extremely careful. If possible, clean the old heat sink compound off the CPU and heat sink. Fix any problems you find, reseat the CPU, put new heat sink compound on the CPU and heat sink, and mate the CPU to the heat sink.

If that doesn't solve the problem, a damaged CPU, motherboard, or RAM socket is likely.