Would like to understand RAM in the context of a boot.ini switch...

[Caveman]

It's a DELL 390 with 4GB of RAM... System properties reads 3.25GB af RAM. Not too concerned about that but... Please help me set the following straight:

1) If a machine has 8GB of RAM, only 2GB are accessible by the (Win XP 32bit) OS. Yes?

2) If a 3GB "boot switch" is added to the boot.ini file, there can be up to 3GB available for software applications to use... Yes?

3) Regarding 2) above... Is this additional memory "physical" memory or "virtual" memory...?

4) What's the best way to understand "virtual" memory?

 

[AndyHui]

1) The amount of RAM that can be addressed by the OS depends on which particular version you are using. In the case of regular 32bit WinXP Home or Pro, they can address a maximum of 4GB of RAM. Some server versions (eg Win2003 Advanced/Enterprise) can address 8GB or more.

This 2GB figure is the amount of RAM available to a particular process, not the OS as a whole.

Normally, the applications will use the lower 2GB while the upper 2GB of address space is reserved by the OS.

2) The 3GB boot switch increases this 2GB figure as explained above, to 3GB. This is only useful for applications that can truly take advantage of the additional address space, such as database servers. The application must be specifically built for the 3GB switch in order to take advantage of this.

Unless you know that you are running one of these programs, there is no point in setting this switch.

From the above, the 3GB switch reduces the OS reserved address space to 1GB.

3) Neither. It's simply address space available to the application, and doesn't really have anything to do with physical or virtual memory.

4) Read more.

 

[Steve]

Virtual Memory in Windows XP

 

[Caveman]

Thanks much for help!