Half Memory not detecting

Hello Everyone,

I'm having an issue with my PC and was hoping someone could help me out.

Summary:

I currently have 8GB (4GB x 2) RAM installed on my PC, however only 4 gb is being shown in windows (Total 4gb (usable 3.45 gb)). At first I thought it was a connection problem, but I tried reinserting, switching, nothing worked. In the bios also on 4096mb is showing as memory, however, it is detecting the other 4096mb ram, but under enabled it is blank. (refer to picture)

http://imgur.com/a/AugkR




Specs:
AMD A10 7850k (3.7 ghz)
Gigabyte FM2A55M - DC2 (rev 3) mobo
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 2133 (PC3 17000) Desktop Memory
Zotac GTX 750 ti 2GB DDR5
650w PSU (rated 80+)
128GB SSD + 1TB HDD
Win 10 (64 BIT)

Steps taken so far:
Firstly, third party applications such as cpuZ and rammon are detecting both the modules without any issue, They are listing all the information and showing total RAM as 8GB.
Running Memory diagnostic tool also didn't throw any error.


Searching online, people have faced this issue, however I cant find any solution that will resolve this.

From the bios;
I manually increased the frequency to 2133mhz
Also upped the Dram voltage to 1.6v
Also tried to up the nbcore voltage to +0.1 v
Maually set the time to 11-11-11-30.
Tried enabling the XMD mode (I dont recall the exact name, but its for faster memory)
Updated the bios version


I spent almost two hours in the bios, but nothing worked. (PS: I don't know much about OC and haven't played around in bios before, was following whatever I found online)
Loaded defaults after all failed.

Further;
I took out my CPU to confirm there was no bent pins (looked good)(had to apply thermal paste again )
Took out the CMOS battery for quite some time, hoping it would reset some stuff.



I was hoping one of you smart men could help me out here. There are 2 ram slots in the motherboard. The bios/os is only detecting the first one! If I only put RAM on the second slot, the computer won't boot. Now I know, a-lot of you would be thinking that it is a faulty slot. I honestly doubt it. Reason being, all the other software are recognizing the ram, reading all its readings. Even the Bios is recognizing the RAM, but under enabled its ---. (Check the picture).

Giving up here, you guys are my last hope!