| 1 | | It's normal. When it was first introduced, PAE was unlocked for every version of Windows, including XP. With PAE the page frame number field was expanded from 20 to 24 bits. The size of the "byte offset" from the address being translated is still 12 bits, though, so the total physical address size increases from 32 bits to 36 bits, from 20+12 to 24+12. This increased the physical memory addressable by the CPU from 4 GB to 64 GB and the OS programs still work at 32bit thanks to the HAL (hardware abstraction layer). Unfortunately, though, many manufacturers didn't officially support PAE for their home tier products and this led to many incompatibies with the normal 32bit drivers, especially with system with a large amount of RAM, so Microsoft decided to artificially limit PAE to ~3.5 GB to prevent these issues in some version of Windows, leaving other version unlocked, like Windows Server. My version of Windows XP Professional is unlocked and also gets updates from Microsoft with the paid Extended support renewed every year, but a normal version of Windows XP doesn't. |
| | 1 | It's normal. When it was first introduced, PAE was unlocked for every version of Windows, including XP. With PAE the page frame number field was expanded from 20 to 24 bits. The size of the "byte offset" from the address being translated is still 12 bits, though, so the total physical address size increases from 32 bits to 36 bits: from 20+12 to 24+12. This increased the physical memory addressable by the CPU from 4 GB to 64 GB and the OS programs still work at 32bit thanks to the HAL (hardware abstraction layer). Unfortunately, though, many manufacturers didn't officially support PAE for their home tier products and this led to many incompatibies with the normal 32bit drivers, especially with system with a large amount of RAM, so Microsoft decided to artificially limit PAE to ~3.5 GB to prevent these issues in some version of Windows, leaving other version unlocked, like Windows Server. My version of Windows XP Professional is unlocked and also gets updates from Microsoft with the paid Extended support renewed every year, but a normal version of Windows XP doesn't. |
