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Figure 1 General Memory Limits

32-Bit Models64-Bit Models
Total virtual address space (based on a single process)4GB 16TB
Virtual address space per 32-bit process2GB (3GB if system is booted with /3GB switch)4GB if compiled with /LARGEADDRESSAWARE (2GB otherwise)
Virtual address space per 64-bit processNot applicable8TB
Paged pool470MB128GB
Non-paged pool256MB128GB
System Page Table Entry (PTE)660MB to 900MB128GB
Figure 2 Physical Memory and CPU Limits

Physical Memory and CPU Limits32-Bit Models64-Bit Models
Windows XP Professional4GB (1-2 CPUs)128GB (1-2 CPUs)
Windows Server 2003, Standard Edition4GB (1-4 CPUs)32GB (1-4 CPUs)
Windows Server 2003, Enterprise Edition64GB (1-8 CPUs)1TB (1-8 CPUs)
Windows Server 2003, Datacenter Edition 64GB (8-32 CPUs) 1TB (8-64 CPUs)
Figure 3 Changes to PE File FIelds

Header FieldChange
Magic Set to 0x20b instead of 0x10b
BaseOfDataDeleted
ImageBaseWidened to 64 bits
SizeOfStackReserveWidened
SizeOfStackCommitWidened
SizeOfHeapReserveWidened
SizeOfHeapCommit Widened
Figure 4 New 64-Bit APIs

FunctionalityAPI
Exception HandlingRtlAddFunctionTable RtlDeleteFunctionTable RtlRestoreContext RtlLookupFunctionEntry RtlInstallFunctionTableCallback
RegistryRegDeleteKeyEx RegGetValue RegQueryReflectionKey
NUMA (Non-Uniform Memory Access)GetNumaAvailableMemoryNode GetNumaHighestNodeNumber GetNumaNodeProcessorMask GetNumaProcessorNode
WOW64 RedirectionWow64DisableWow64FsRedirection Wow64RevertWow64FsRedirection RegDisableReflectionKey RegEnableReflectionKey
Miscellaneous GetLogicalProcessorInformation QueryWorkingSetEx SetThreadStackGuarantee GetSystemFileCacheSize SetSystemFileCacheSize EnumSystemFirmwareTables GetSystemFirmwareTable
Figure 5

RAX
RBX
RCX
RDX
RSI
RDI
RSP
RBP
R8
R9
R10
R11
R12
R13
R14
R15