not all RAM "usable"

[Habedrabbo]

specs:
MOBO:gigabyte 990fxa-ud3 rev 4
RAM:G-Skill Ripjaws(2x4GB) 1600
PSU:Gigabyte Greenmax plus 550W 80+ bronze
CPU:AMD FX8350
GPU: Sapphire Radeon R9 280
OS: Windows 8.1 64bit

Problem:

The issue is as stated in the thread title. I go to properties and find that 8GB of memory are detected but only 3.92GB is "usable." And yes they are seated properly; I know Google is my friend, but the "solutions" I have found are not working. The common solution I have found is going to msconig and changing the max setting in the advanced boot RAM options.
This hasn't worked, I've also tried to make some changes in BIOS but I'm no computer tech so I don't know which to switch. I've just been changing options that sound like they would make an effect but that's not the case. Another answer i have read is that there might be a bad stick of RAM but no, both boot up fine by them selves and the system detects 8GB's.
I have also looked at Gigabyte's compatibility with the RAM but according their site the info is outdated and they don't want to put all the RAM info. out there since there's so many options(don't blame them). So unless I'm missing something completely obvious to the pro's eyes than an amateur like me hasn't seen or tried please go ahead and suggest. I'm just a little irritated I spent about 70 USD on this RAM and cant seem to use it all.

NOTE: This is a new build and my first any suggestions about the problem or enhancing the overall system in it's current state in anyway is greatly appreciated. Also; haven't read any where that this would even be a problem but, I have updated and downloaded all current drivers.

 

[Pinhedd]

Just thought of this but my GPU is a 3gb version, could that be it?

Nope. Please follow the advice in my previous post. Figure out how much memory the firmware is able to initialize. If it initializes only 3092 then you have either a faulty DIMM or a faulty DIMM slot.

 

[Habedrabbo]

In BOIS there is a total of 8192MB of memory freq. 1608.XX system memory multiplier is 8.00

 

[Habedrabbo]

I also chacked the info in the AMD catalyst and this says
Installed Memory:8gb
Total physical:3.96gb
Available physical:2.35gb
Total virtual:11.2gb
Available virtual:8.49gb
"Page file space":7.25gb

 

[Pinhedd]

I also chacked the info in the AMD catalyst and this says
Installed Memory:8gb
Total physical:3.96gb
Available physical:2.35gb
Total virtual:11.2gb
Available virtual:8.49gb
"Page file space":7.25gb

Yeah that's pretty consistent with a faulty DIMM or DIMM socket. The 8GiB is coming from the SPDs, not the total amount mapped into the address space.

Check each DIMM in each socket, make sure that every combination works.

 

[Habedrabbo]

so I took out the bad stick and my computer is noticeably slower, is there any harm in leaving the bad RAM in the DIMM slot? because while it was in my computer was definitely faster.

 

[Pinhedd]

so I took out the bad stick and my computer is noticeably slower, is there any harm in leaving the bad RAM in the DIMM slot? because while it was in my computer was definitely faster.

That's a placebo effect. The bad stick wasn't doing anything. The firmware could read the SPD (which is just a ROM) but it wasn't able to initialize it and thus it was never mapped into the physical address space. It was just sitting there doing nothing, and once removed it will still be sitting there doing nothing.

You should setup an RMA with G.Skill. Tradesman1 knows a ton about G.Skill so he may be able to point you in the right direction.

 

[Habedrabbo]

Well thanks for the knowledge and your help.

 

[Pinhedd]

You're most welcome.