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I have Windows XP Pro 32bit, and cannot upgrade to a 64bit os for various reasons at the moment. I read that I can use PAE to remove the 3.5Gb limit of a 32bit os by editing the boot.ini file.

Is this true, if it is true, how do I edit the my system so I enable the PAE?

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marked as duplicate by Heptite, Kevin Panko, Moses, Excellll, Dave Apr 8 '14 at 14:44

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@Moab : What about this? You can obtain usbport.sys by downloading windows server 2003 service pack 2. Then extract which is in the cab format... – user2284570 Apr 4 '14 at 21:19
up vote 5 down vote accepted

Consumer 32-bit versions of Windows are limited to 4GB of RAM and PAE will not help you at all. As a side note PAE itself has been enabled since WinXP Service Pack 2 if I remember correctly, this was done to enable support for the NX Bit which is a security enhancement offered by PAE.

Windows is licenced by Microsoft and that licence includes a memory limit. In all home 32-bit versions of Windows the maximum limit is 4GB.

It is theoretically possible to use more, but in practice is it breaking the terms of your licence and may or may not break your system as well.

PAE does allow an operating system to use up to 64GB of RAM, but Microsoft chose not to allow it because it would break almost every device driver that was not PAE aware. They did this for your own good.

There's a SuperUser Blog post about this as well.

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Its a kernel limitation in Windows, someone hacked the W7 kernel to allow over 4gb in 32bit Windows – Moab May 6 '11 at 14:58
@Moab, that's why I stated it as a licensed memory limit rather than a hard memory limit and linked to a page similar to yours where the guy had basically worked around the limit in software at the cost of putting the kernel into "test mode" along with host of potential PAE-related problems. Thanks for the link, I could have sworn I'd seen a program that lifted the limit for you but couldn't find it for the life of me and there it is right in your link... – Mokubai May 6 '11 at 15:05
@Mokubai : As far As rember SP2 enabled PAE along DEP... In SP1 You can use >4Gb by default by adding the /PAE switch to boot.ini... – user2284570 Apr 4 '14 at 19:26
@user2284570 No, PAE is enabled only in order to support the NX bit to enhance OS security via DEP. It is NOT enabled in order to support large memory configurations nor are you actually able to use more than 4GB in 32-bit versions of Windows outside of the server market. – Mokubai Apr 5 '14 at 13:13
@user2284570 From Wikipedia "The no execute (NX, or XD for execution disable) bit resides in bit 63 of the page table entry and, without PAE, page table entries on 32-bit systems have only 32 bits; therefore PAE mode is required in order to exploit the NX feature. However, "client" versions of 32-bit Windows (Windows XP SP2 and later, Windows Vista, Windows 7) limit physical address space to the first 4 GB for driver compatibility " Hence it is possible but almost certainly not enabled for the home market. – Mokubai Apr 5 '14 at 13:18

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