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Figure A-2 shows the approximate amount of directly-addressable memory available with various
Windows operating systems.
Figure A-2: Memory limits with Windows operating systems
While 32-bit Windows operating systems can address a maximum of 4 GB directly, memory space
can be extended with certain operating systems through the use of Address Windowing Extensions
(AWE).
Windows Server 2003 introduced 64-bit addressing, shattering the earlier 4 GB direct-addressing
limitation. Windows Server 2003 Datacenter Edition can address 512 GB directly – and up to
256 TB indirectly.
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