AMD64 Guide, Meaning , Facts, Information and Description

The AMD64 is a 64-bit processor architecture invented by AMD. It is a superset of the x86 architecture, which it natively supports.

Table of contents

1 Architecture overview 2 Operating modes 3 AMD64 market analysis 4 Implementations 5 See also 6 External links

Architecture overview

TODO: write about the AMD64 architecture. New instructions, capabilities, register sizes, etc.

• NX Bit The NX Bit is a processor feature that prevents certain kinds of malicious software known as worms from taking control of a computer via a software attack known as a buffer overflow.

There are two versions of the A64 aside from the socket 754 (older) and socket 939 (newer). In addtion, the older versions of A64 use 130 nm transistors while the newest A64's use 90 nm transistors. Because of this AMD has been able to shrink the die size while still maintaining low heat output. One test has shown a 90 nm processor being overclocked to 1.45 times its stock speed.

Due to the larger width for address space, the AMD64 architecture can address up to 256 terabytes of memory. Future implementations of the AMD64 architecture may provide up to 2 exabytes of available memory.

Operating modes

TODO: Write about the operating modes, and the capabilities of each.

AMD64 Has five operating modes.

1. legacy 16bit mode
2. legacy 32bit mode
3. compatibility 16bit mode
4. compatibility 32bit mode
5. true 64bit mode

Legacy mode cannot run 64bit programs. Compatibility mode can switch between 64 and non-64 bit programs (penalty)

AMD64 market analysis

AMD64 represents a break with AMD's past behavior of following Intel's standards, but follows Intel's earlier behavior of extending the x86 architecture, from the 16-bit 8086 to the 32-bit 80386 and beyond, without ever removing backwards compatibility. The AMD64 architecture extends the 32-bit x86 architecture (IA-32) by adding 64-bit registers, with full 32-bit and 16-bit compatibility modes for earlier software. Even the 64-bit mode is largely backward-compatible, allowing existing tools targeting x86 (eg. compilers) to be retargeted to AMD64 with minimal effort. The AMD64 architecture also features the NX bit.

Implementations

The following processors implement the AMD64 architecture:

• AMD Athlon 64
• AMD Athlon 64 FX
• AMD Opteron
• Intel Xeon (some models)
• Intel Pentium 4 (some models)

See also

• NX
• EM64T (Intel's implementation of the AMD64 architecture)

External links

• AMD's technical documentation for the AMD64 architecture
• Free AMD64 documentation on CD-ROM (US, Canada only), and download format

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