Windows 10: I have 16 GB of RAM but only 6.94 GB usable?

I had a look at my system information and I noticed that I only have 6.94 GB usable RAM but 16 GB is installed.

I recently decided to overclock my PC from 3.70 GHz to 4.19 GHz, I thought that was the issue, but I'm not sure why I thought overclocking would affect usable RAM. I tested it out anyway and there was no change.

Before I upgraded my GPU I had more "usable" RAM but I can't exactly remember how much it was. It was definitely over 8 GB.

Screenshot by Lightshot

Specs:
Motherboard: A88X-G45 (MS-7900)

CPU: AMD A10-7850K APU

RAM: Kingston HyperX FURY (4x4 GB, 16 GB total)

OS: Windows 10

GPU: Radeon RX 480 GDDR5 8 GB


Resource Monitor shows the space for "Hardware Reserved" physical memory is 9277 MB.
Screenshot by Lightshot

Here are some screenshots of CPU-Z Memory tab and SPD tab.

Memory tab:
Screenshot by Lightshot

SPD tab:
Slot #1 - Screenshot by Lightshot
Slot #2 - Screenshot by Lightshot
Slot #3 - Screenshot by Lightshot
Slot #4 - Screenshot by Lightshot

:)

 

3.46G Usable instead of 6 gb ram

Previously, I have installed 32 bit version of Windows 10 when my ram is 4 gb (1.71gb Usable), after it, I installed 64 bit version of windows but the usable ram is not icreasing. I upgraded the ram to 6gb but the usable ram is 3.46g, I want to increase
the usable RAM size, anyway?

 

winodws 10 24 gb ram installed only 16 usable

I just upgraded from win 7 home premium 64 bit to win 10

I know that the windows 7 version I had only went up

to 16 gb of ram but I thought that Windows 10 had up

to 128 gb limit.

It still shows in the system that 24 gb is installed but only 16 is usable

anyway to fix this, or do I need to try and create an install disk to do

a clean install?

My mb supports up to 32 gb ram

 

Why 2.66 GB usable in 4 GB ram?

Thanks to everyone for their valuable suggestions. I guess the problem was with the OS.Because after increasing my ram from 4 gb to 8 gb still the usable memory was 2267 mb out of 8 gb, then I did a clean install of Windows 7.Now everything is fine and smooth, and usable memory is 7.9 gb out of 8 gb.