Need a hand - 8Gb Hardware reserved memory

Hi all,

So I've got 16Gb of RAM in two sticks of 8Gb, and half of it seems to be unusable. My BIOS can see both sticks, and confirms the size, speed etc - but insists that only 8Gb is available. Windows similarly can see 16Gb total, but claims that 8Gb is "Hardware Reserved".

Haven't really found any clues as to what could be reserving eight gigs of memory. At the moment it seems possibly an issue with the BIOS - I tried updating it to the most recent version available, without much luck. Does anyone have any insight as to what might be going on here?

Here are some specs:

Mobo is a Sabertooth 990fx r2.0, with a Phenom II X6 1100T processor (3.3GHz, 6-core) and a GeForce GTX 560 Ti graphics card.

The RAM sticks themselves are a pair of 8 gig DDR3 Corsair sticks - managed to find the same ones on the interwebs, so I'll link them to make sure I'm not missing any info:

They're currently installed into slots 1 and 3, with slots 0 and 2 being empty.


Anyway, if any of yall could give a hint as to what might be causing this, it'd be appreciated ;D

I would primarily suspect some memory mapping setting in the BIOS. I skimmed through the manual but couldn't spot a clear suspect, but it's quite possible that a setting or two is not in the manual. I don't know about this exact board but in the past there has been options required for full compatibility with some server systems, that have happened to have its default value set so that it can limit the amount of RAM usable on regular Windows machines.

It's also possible for speed and voltage settings to be off in a way to produce that symptom, but I wouldn't suspect that here.

What OS are you using?