Available memory less than half of my Installed physical memory?

[danznewty]

I've just looked at my system information and discovered the stats below:

Installed Physical Memory (RAM) 4.00 GB
Total Physical Memory 3.19 GB
Available Physical Memory 1.99 GB

I'm a complete novice with hardware so can anybody explain why this is?
Does this mean Im only running with 2GB of ram?

 

[neon neophyte]

32 bit windows? im guessing you dont have a discrete video card either. something built in that shares system memory

 

[aldan]

is your operating system a 32bit version by any chance?

 

[Dblkk]

Well, anything that's running or in the background running takes away from memory. Windows a chunk, any antivirus including windows takes a large chunk. I have 16gb memory in, 2 webpages open and ive only 9.4gb available. Graphics also takes a chunk, especially if its onboard graphics, aka using the cpu for display vs having a dedicated card.

 

[danznewty]

no, win7 64 bit.

I've also accidentally championed an answer. Please disregard this.

 

[neon neophyte]

and your video card?

 

[danznewty]

Well, anything that's running or in the background running takes away from memory. Windows a chunk, any antivirus including windows takes a large chunk. I have 16gb memory in, 2 webpages open and ive only 9.4gb available. Graphics also takes a chunk, especially if its onboard graphics, aka using the cpu for display vs having a dedicated card.

Ahh I see. Available memory is what is not being used at this moment in time, I dont know why that wasnt obvious to me.

But I still dont understand the total physical memory figure of 3.19GB?

 

[danznewty]

and your video card?

GeForce 9400 GT.

 

[neon neophyte]

oh, hmmmm. 9400 is a discrete video card isnt it?

like, its a card that you can physically pull out of your computer?

 

[danznewty]

oh, hmmmm. 9400 is a discrete video card isnt it?

like, its a card that you can physically pull out of your computer?

Yes. Pretty ancient thing too.

 

[Pinhedd]

Well, anything that's running or in the background running takes away from memory. Windows a chunk, any antivirus including windows takes a large chunk. I have 16gb memory in, 2 webpages open and ive only 9.4gb available. Graphics also takes a chunk, especially if its onboard graphics, aka using the cpu for display vs having a dedicated card.

Ahh I see. Available memory is what is not being used at this moment in time, I dont know why that wasnt obvious to me.

But I still dont understand the total physical memory figure of 3.19GB?

32 bit consumer editions of Windows have their physical address space limited to 4GiB. 64 bit editions of Windows and 32 bit server editions do not have this same limitation. They are still limited, but to a much higher value.

The bulk of the physical address space is allocated to primary memory in the form of DDR3 SDRAM, but IO devices and hardware systems tend to expose their functionality through a process known as memory-mapped IO. The operation of memory mapped devices is exposed through memory addresses in the same way as SDRAM. When 4GiB of SDRAM memory is installed in a system that uses a 32 bit physical address space the entire address space would be consumed by the SDRAM alone leaving no room for other devices. As such, memory mapped devices displace the SDRAM in the physical address space such that the SDRAM rolls past the 4GiB address barrier. In a system that performs memory remapping or does not have a 4GiB barrier this is not an issue, but in 32 bit consumer versions of Windows this functionality is disabled. As such, any SDRAM displaced by memory-mapped devices is disabled.

In simpler terms, consider the following. A system has a strict 4 GiB address space (no PAE, no remapping). The system hardware reserves 1GiB worth of addresses for its own purposes, leaving 3GiB worth of addresses left. The user installs 4GiB of memory, but the firmware can only map 3GiB of it into the addressable space.

The simple solution is to use a physical address space that is larger than 32 bits and this has been the standard dating back to 1995 when it was extended to 36 bits or higher but many operating systems keep it clamped at 32 bits for compatibility and marketing reasons.