All processes (e.g. application executables) running under 32 bit Windows gets virtual memory addresses (a Virtual Address Space) going from 0 to 4,294,967,295 (2*32-1 = 4 GB), no matter how much RAM is actually installed on the computer.
In the default Windows OS configuration, 2 GB of this virtual address space are designated for each process’ private use and the other 2 GB are shared between all processes and the operating system. Normally, applications (e.g. Notepad, Word, Excel, Acrobat Reader) use only a small fraction of the 2GB of private address space. The operating system only assigns RAM page frames to virtual memory pages that are in use.
Physical Address Extension (PAE) is the feature of the Intel 32 bit architecture that expands the physical memory (RAM) address to 36 bits (see KB articles 268363 and 261988). PAE does not change the size of the virtual address space, which remains at 4 GB, just the amount of actual RAM that can be addressed by the processor.
The translation between the 32 bit virtual memory address used by the code running in a process and the 36 bit RAM address is handled automatically and transparently by the computer hardware according to translation tables maintained by the operating system. Any virtual memory page (32 bit address) can be associated with any physical RAM page (36 bit address).
Here's a list of how much RAM the various Windows versions and editions support (as of Nov 2004):
Windows NT 4.0: 4 GB
Windows 2000 Professional: 4 GB
Windows 2000 Standard Server: 4 GB
Windows 2000 Advanced Server: 8GB
Windows 2000 Datacenter Server: 32GB
Windows XP Professional: 4 GB
Windows Server 2003 Web Edition: 2 GB
Windows Server 2003 Standard Edition: 4 GB
Windows Server 2003 Enterprise Edition: 32 GB
Windows Server 2003 Datacenter Edition: 64 GB
mặc dù biết máy Dell E support tới 4G lận nhưng vẫn thấy run run, hỏi ý kiến các bác trước xem sao 
Thanks
. Nói tóm lại Ram đồng bộ là tốt nhất.
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