4GB memory limit

Lee H

Hi

I read this

WinXP only has 4GB of physical memory addresses. Some of those addresses are taken up by hardware interfaces (the number depends on the MB design, expansion cards, etc). Only the leftover addresses are available for accessing actual physical memory, hence the less-than-4GB value you see.


Q. If the hardware interfaces are taking some of the 4GB and XP then shows whats left, how come when you have 2GB it doesnt do the same.

Any info would be great

Lee

bighornsheep

Lee H wrote:

Q. If the hardware interfaces are taking some of the 4GB and XP then shows whats left, how come when you have 2GB it doesnt do the same.

Your question is worded sort of strange, maybe I'm not understanding it properly. Firstly, the 4GB limitation has to do with the fact that it's a 32-bit OS running on a 32-bit CPU, therefore the MAXIMUM addressing memory space is 4GB. The "addresses taken up" that you're talking about depends on the operating system, and machine design, generally the OS has a memory manager, process manager, file manager, and I/O controller that sits in a section of the memory space called an offset that handles the core functionalities, in addition, other devices such as the hard drive, and graphics card may be given "dedicated" memory space with Direct Memory Access ability.

The above is a "general" concept of how any OS will operate, but despite 4GB, or 2GB, even if you only have 512mb of RAM installed, XP still has a 4GB addressable memory space.