Many people will tell you that it is not possible to run at 32 bit version of XP with more than 3 GB Ram. They say that XP would not recognize the Ram above the 3 GB – actually for most of you XP will show the 3 GB as 2,5.
They are wrong! XP is a 32 bit version, which means it supports up till 4 GB. Just do a little calculation and you will see that I am right in my suggestion.
232 = 4.294.967.296
4.294.967.296 / (1.024 x 1.024) = 4.096
To get XP to recognize the remaining Ram you have to do a little trick. In the boot.ini (hidden file, which is found in the root of c) you have to add some new switches /3GB and /PAE.
Per default the user-mode memory space is limited to 2 GB with the /3GB it will be limited to 3 GB. This switch is a feature from the Windows 2000 / 20003 servers and was introduced to XP, so that device-driver developers could test their drivers without have to install a Windows server.
Note this switch should be used with caution; it can cause applications to have address dependencies related problems. Also it can cause an error with Active Directories (resource starvation). Though, these problems are mostly seen on a Windows 2003 Server.
By using the /PAE switch, it will let your device drivers use the Ram up till the 4 GB.
These changes may not work on all chipsets, cpu’s, motherboards. But after I enabled the switches, I’m able to see 3,5 GB and it seams that XP is using the ram above the 3 GB when I am looking on the usages in the Task Manager 🙂