Kewlx25 said:
"32-bit recognizes at most 3.5GB"
that's *at most*, it may see less.
Actually, it could be slightly more than 3.5GB. Keep in mind the OS is not responsible for "seeing" or "addressing" memory. The BIOS and hardware (chipset) does all that, then reports what is available to the OS via industry standard
memory map (e820). The OS just uses whatever the BIOS says is available for it.
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EVERY device in your computer consumes a memory range. The biggest being your video card. If you get a dual 1GB SLI/xfire video card that shows 2GB total, then your 4GB of ram will only be 2GB of ram.
Not so. The biggest consumer of address space are the Southbridge devices. e.g. Intel's documents describe that its recent ICH Southbridges require approx. 750MB address space with typical integrated or onboard devices, before any expansion cards are installed including graphics.
Graphics cards with more than ~256MB RAM do not map VRAM into processor address space on a 1:1 basis. Typically, they reserve a 256MB window for each GPU, and implement techniques such as bank-switching to reach all the RAM. See:
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The Growth of VRAM
Another factor in the PC memory equation has been growing as well: video memory size. In the early days of Direct3D, the typical video card had 16 or 32 MB of Video RAM (VRAM). High-end video cards now have 512 MB, 640 MB, 768 MB, or more VRAM. When video cards had 16 or 32 MB of Video RAM, this memory was mapped directly into every process that used Direct3D for efficient access by the application and video driver.
As video cards grew larger, this became unsustainable. A 768 MB hole in the 2-GB virtual address space of each process would leave very little space for applications. Similarly, taking 768 MB out of the 4 GB physical address space would be too constraining. This problem is exacerbated in dual GPU configurations (SLI®/Crossfire™).
Therefore, video card manufacturers typically implement a 256 MB physical memory window for the video graphics memory, and modern drivers do not create direct process mappings for the entire VRAM size. Process address space is still consumed for working with the AGP aperture (64 MB, 128 MB, or more typically on modern game systems 256 MB in size). While PCIe uses a dynamic aperture, it too is mapped into each process that uses Direct3D. --
RAM, VRAM, and More RAM: 64-Bit Gaming Is Here
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Very few 32bit programs shouldn't run in Vista/Win7 64. If they don't run it's because they're poorly programmed.
Or because they still use legacy code such as 16-bit that are commonly found in installers, et. al. I have a couple dozen BIOS and other utilities that still use 16-bit code, and there are no good 32-bit or 64-bit alternatives to them.
No matter what the reason is, if you've spent $1700 on applications a couple years ago that don't work correctly on 64-bit OS and the software vendor's solution is for you to purchase their newer 64-bit compatible version, then you still need 32-bit OS or must run 32-bit OS in a virtual machine (which isn't always possible, either).