4gb of memory showing up as 3.3gb

[Ssshaker]

Hi all,
I have just installed 4x1gb RAM chips in my motherboard but is only showing up in Device Manager as 3.01 and the BIOS as 3.4gb.
I have run Belarc Advisor and it says 4 slots each containing 1gb. I also put 2 chips only in Dual mode which revealed 2gb, then replaced them with the other two chips which also showed as 2gb so the chips are fine
The board is Gigabyte GA-8IPE775-G which is dual-channel (2 x 2 slots)
Is there some tweak I should know about or maybe I need to flash the BIOS?
Hope someone can help me here.
Thanks.....S

 

[micker377]

What type of video card do you have? It might be "shared" memory.

 

[Ssshaker]

Hi Mick...awfully big VGA chip to grab that much memory

The board is non-integrated, VGA is stand-alone 128mb. I have just checked Gigabyte web site and I already have the latest BIOS installed so no luck there.
Thanks......

 

[Frank4d]

Stolen from another forum:
Almost all systems put the PCI Memory Mapped IO window into the 3.75-4GB region of the physical memory map. The registers for the APICs and other system resources are also typically in this region. Now with PCI-Express, the Memory Mapped PCI config registers are typically being mapped in the 3.5-3.75GB range. The memory controllers, host bridges,
north-bridges, and/or whatever else glues the memory to the bus to the CPU decode these addresses into PCI cycles, not RAM cycles. Some systems are smart and re-map the RAM that is hidden by these holes into a region >4GB. Some systems are dumb, though, and just deny you access to the RAM that is covered up. It's very much like the old days of the
XT/AT architecture when you had 1MB of RAM but everything above 640k was hidden by the VGA framebuffer, ISA option ROMs, and system BIOS, but some systems where smart enough to relocate the hidden RAM.

So, your missing .5GB is almost certainly not due to defective RAM, it's just due to The Way Things Are. It's a lot harder for Opteron systems to be smart about this than Xeon systems since all of the remapping magic can happen in the hostbridge on the Xeon, while the Opertons need to have their built-in memory controllers programmed specially for it.

 

[Ssshaker]

Hi Frank...thanks very much for that! Certainly makes sense (or nonsense). I presume with 64bit O/S that will be a Thing Of The Past instead of The Way Things Are
Thanks again...S

 

[dbMark]

All 32-bit boards max out at somewhere under 4 GBs. The theoretical limit is 4 GB, but in reality some of those addresses are needed by the system, whether the board, video or whatever. This is exactly the reason why 64-bit systems are coming out now - while most individual programs may not need it, huge memory does. In time, perhaps taking a few decades, their memory limits will approach the astronomical max for 64-bits: 16 billion billion bytes!

 

[Ssshaker]

Thanks db and to everyone else who shed some light on this topic. I have my answer so will disable notification for this post.
Thanks again guys