hedwards: I'm using a discrete videocard. It's a bloody incompetent mistake if MS is using that memory anyways.

hedwards: I'm using a discrete videocard. It's a bloody incompetent mistake if MS is using that memory anyways.

eyeball226: Well surely it still has to address the memory in the card?

cjrgreen: Some (but not all) of that memory has to be mapped into your address space; otherwise there would be no way to transfer data to or from the GPU.

Windows does this with "apertures". In the old AGP days, Windows made the aperture setting visible. Now it uses multiple apertures of whatever size it thinks it needs.

Apertures show up in your display adapter's memory statistics as "shared system memory" under Vista and W7.

For example, my old 8800 GTS 512, which I know doesn't have more than 512MB memory, shows up in Vista as having 576MB. The additional 64MB is the aperture that Windows uses to copy data in and out.

The fact that it shows up as "576MB" is just an artifact. 512MB of that memory is on the card where it isn't addressed by Windows, and 64MB is in system space where Windows can copy to and from the 512MB on card.

hedwards: Yes, but it's something funky. In moving up from 512mb of video RAM to 1024mb of video RAM, the amount of total physical memory available didn't change at all.

My point was that MS claims to support the RAM without actually bothering to mention that it's supported but you can't actually use all of it. It's an architectural limitation, I just don't like the lack of honesty on their part regarding the issue. If they claim to support it then it should be usable.

Yes, I did kind of word that badly.

cjrgreen: Microsoft does clearly state that you cannot use the full 4GB on a 32-bit setup. They never claimed to be able to access 4GB of RAM in 32-bit space.

AndrewC: Devices have to map their memory below 4 GB for compatibility with non-PAE-aware Windows releases. Therefore, if the system has 4GB of RAM, some of it is either disabled or is remapped above 4GB by the BIOS. If the memory is remapped, X64 Windows can use this memory. X86 client versions of Windows don’t support physical memory above the 4GB mark, so they can’t access these remapped regions. Any X64 Windows or X86 Server release can.

X86 client versions with PAE enabled do have a usable 37-bit (128 GB) physical address space. The limit that these versions impose is the highest permitted physical RAM address, not the size of the IO space. That means PAE-aware drivers can actually use physical space above 4 GB if they want. For example, drivers could map the “lost” memory regions located above 4 GB and expose this memory as a RAM disk.

In short, XP and Vista can truly manage ~4GB of physical RAM, but shows only the "available" ram. If you have a onboard vídeo with 512mb and something else on-board to complete 1gb, your manager will show only 3GB "available".

hedwards: No, MS definitely doesn't state that clearly. There are references to what you can do to use more RAM than that, and even the page where they cover the memory limits indicates that at least from 2k on that they support 4gb of RAM.

It's somewhere between misleading and fraudulent to claim that 4gb of RAM is supported, but fail to mention in the same place that the memory isn't actually addressable.
hedwards: That sounds about right, the information on MS' site is confusing, references to physical limits, PAE and memory beyond the 4GB threshold.

It doesn't matter a whole lot to me, but the whole issue is hardly one which is easily understood by people not specifically interested in it.

Navagon: 64bit is pretty much mandatory now. You'll just have to take any incompatibilities in your stride. But no GOGs should have any (additional) problems due to you using a 64bit OS. Windows 7 64 has very good 32bit support.

hercufles: thanks i have 64 bit now love to see my pc using all the memory now, now my only concern is getting the audio to run :)

hercufles: thanks i have 64 bit now love to see my pc using all the memory now, now my only concern is getting the audio to run :)

KavazovAngel: Download a 64bit driver for your sound card.

AndrewC: Also, some more context to the whole memory allocation thing.

Starting with the 80.xx driver series, NVIDIA's display drivers when used with 32-bit systems that used physical memory addresses higher than 0xffff`ffff would fail. The system would boot, kinda, but the drivers truncated 64-bit physical addresses, causing them to overwrite essentially random bits of physical memory, with massive display corruption and instability.

Rather than dictate that 32-bit drivers should properly handle 64-bit physical addressing, Microsoft altered desktop versions of 32-bit Windows, starting with Windows XP Service Pack 2, so that any physical memory with an address higher than 0xffff`ffff would simply be off-limits. This meant that the drivers never had to cope with high memory addresses, and so that particular bug would never manifest itself.

The repercussion of this is that systems with modest amounts of memory (typically 3 GiB or more) and medium-to-high-end video cards generally cannot use all of their RAM when used with 32-bit desktop Windows. The video card memory is generally mapped, at least in part, to physical addresses below 0xffff`ffff, pushing some amount of RAM to physical addresses above 0xffff`ffff. This RAM is then off-limits to 32-bit desktop Windows.

pops117: Thank you for that bit of information! I didn't know the specifics about that particular issue, I often wondered how Windows allocated the available address space and video card memory space...