3gb usable out of 4gb 64bit windows

[Stun_Grenade]

As I mentioned in title I have clearly a windows 7 64bit os.
Its showing 3gb usable out of my 4gb ram.
When I checked in bios "pci mmio allocation 4gb to 3072mb"
^ it shows this,( memory remap)
I tried both enabling and disabling I get same issue
I tried installing windows 10 64bit still same issue
Tried searching whole internet and has no clear solution found
I have gtx 750 1gb but that definitely doesn't seem to be the issue.
My motherboard is zebronics zeb-z31, there is no bios update from manufacturer
I tried changing ram slots, tried both tick and untick in msconfig max mem.
Nothing works.
I finally tried taking out one of my ram and it fine detects 2gb ram and all is usable but idk why if I put 4gb it goes to 3gb usable.
Please help if anyone know.

 

[Stun_Grenade]

Actually 4gb was detected and working fine until I installed windows 7 as 10 was slow. And then it started. From that time no matter any windows I install or do anything its stuck at 3gb usable out of 4gb

 

[Pinhedd]

Actually 4gb was detected and working fine until I installed windows 7 as 10 was slow. And then it started. From that time no matter any windows I install or do anything its stuck at 3gb usable out of 4gb

On Windows 8 and newer Windows will show both the amount of memory detected via the DIMM SPDs (little serial chips on the DIMMs that contain information about the DIMM) and the amount of memory that is actually mapped by the motherboard firmware for the OS to use. Windows 7 and older show only the amount usable. You might see something like "4.0GB installed, 3.0GB usable" because of this.

In any event, your motherboard simply isn't mapping 1GiB into the physical address space. This is occurring before the firmware even polls the storage devices for bootable partitions, so it's not a result of any OS.

 

[4745454b]

Correct. The bios doesn't care what copy of windows you have. You can disconnect your hdd and watch the bios still boot. From the model name I would assume it has the G31 chipset, which was the 965 with a few tweaks. The 965 and the P35 are practically identical. My memory doesn't include if it supports 4GBs of ram. I stopped to look it up, according to Intel it should work.

https://ark.intel.com/products/31913/Intel-82G31-Graphics-and-Memory-Controller

I suspect you are right and there is some odd bios thing happening that isn't allowing 4GBs.

 

[Stun_Grenade]

So I'm left with no solution or anything I can try ?

 

[4745454b]

Nothing you haven't tried already. Nothing I know of anyways.