I've been trying to determine whether the 3GB switch is on or off on the system my program is running by calling GetSystemInfo() and checking lpMaximumApplicationAddress on the SYSTEM_INFO struct.
No luck. I think I am doing something wrong.
How do you check whether the 3GB switch is on or not on Windows in C? Code is appreciated.
thanks
Is your program IMAGE_FILE_LARGE_ADDRESS_AWARE ?
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx
Executables that can use the 3-GB address space are required to have the bit IMAGE_FILE_LARGE_ADDRESS_AWARE set in their image header. If you are the developer of the executable, you can specify a linker flag (/LARGEADDRESSAWARE).
Assuming your program is compiled as large address aware, you could simply call GlobalMemoryStatusEx and check the ullTotalVirtual field. If it's larger than 2GB, and you're running on a 32-bit system, then the 3GB flag must be turned on.
I actually have no idea how to 'properly' tell if Windows is natively 32 or 64 bit, but if you have a 32-bit process you could call IsWow64Process to see if you're running on a 64-bit OS.
This all seems a bit indirect, I know :)