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x64 is Microsoft's marketing designation for the Advanced Micro Devices AMD64 and Intel EM64T 64-bit Instruction Set Extensions to the x86 architecture, which were substantially similar as of 2004. Other companies such as Sun Microsystems have also adopted this term.
The "64-bit" designation refers to many aspects of the architecture: the width of the general purpose registers; the widest integer and logical operations supported by the processor; the size of values pushed and popped from the stack; and the width of the pointer data type, or virtual addresses. As of December 2005, current implementations of the x64 architecture only implement the low-order 48 bits of virtual addresses, but pointers are nevertheless 64 bits wide and all 64 bits must be correctly asserted.
As implementations might differ, for instance concerning IOMMU bypass for DMA mapping over 4GB, or additional instructions might be offered in newer processors, use of the x64 designator is mostly intended to signify the mere presence of extensions, rather than endorse specific processor implementations. Thus the x64 appellation does not indicate whether the operating system or software is optimally working with one processor or another.
Internally, x64 versions of Windows use AMD64 moniker to designate various components which use 64-bit technology for IA-32 processors (for example, the system folder on a Windows x64 Edition installation CD is named "AMD64" instead of "i386" in 32-bit versions).
Microsoft products using the name "x64"
- Windows XP Professional x64 Edition
- Windows Server 2003, Standard x64 Edition
- Windows Server 2003, Enterprise x64 Edition
- Windows Server 2003, Datacenter x64 Edition
- Windows Vista x64 Edition (in development)
- .NET Framework Version 2.0 Redistributable Package x64 (64 Bit)
External links
"X64"