8 of 16 GB RAM are hardware reserved

Luggie

Prominent
Jun 22, 2017
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Hi
using msi 970A-G43 mobo with 16GB Crucial Ballistix Sport DDR3-1600 DIMM CL9 Dual Kit and Windows 7 x64 professional.
Task manager only shows 8 GB of it, while Windows Resource manager shows 16, while 8 are hardware reserved. Cpu-z and bios both show 16GB.
I know that when I build my computer half a year ago, it worked perfectly. I didn't change any hardware since then.
Things I tried:
- disabling boot option in msconfig about maximum memory
- searching in bios for any hardware which could reserve memory but didn't come across any
- some odd regedit hint
nothing worked so far for me.
Help highly appreciated!
luggie