AFAIK all AIC's that have physical ram installed have to reserve address space with the OS and with 32bit windows the total is 4gb shared address space. There are supposedly specific apps that utilize PAE to utilize more then 4gb but not anything the avg consumer is probably using.
Don't take it the wrong way but I'm not really sure what position you are in to call others half right and confused considering this issue is clearly documented....
http://support.microsoft.com/kb/929605/
Various devices in a typical computer require memory-mapped access. This is known as memory-mapped I/O (MMIO). For the MMIO space to be available to 32-bit operating systems, the MMIO space must reside within the first 4 GB of address space.
For example, if you have a video card that has 256 MB of onboard memory, that memory must be mapped within the first 4 GB of address space. If 4 GB of system memory is already installed, part of that address space must be reserved by the graphics memory mapping. Graphics memory mapping overwrites a part of the system memory. These conditions reduce the total amount of system memory that is available to the operating system.
The reduction in available system memory depends on the devices that are installed in the computer. However, to avoid potential driver compatibility issues, the 32-bit versions of Windows Vista limit the total available memory to 3.12 GB. See the "More information" section for information about potential driver compatibility issues.
If a computer has many installed devices, the available memory may be reduced to 3 GB or less. However, the maximum memory available in 32-bit versions of Windows Vista is typically 3.12 GB.





Bookmarks