Athlon 64
The AMD Athlon 64 is an eighth-generation x86 microprocessor which implements the AMD64 instruction set first introduced in the Opteron processor. For the first time, Intel's venerable x86 instruction set was extended to 64-bit operation by a competitor, and subsequently cloned by Intel itself in forthcoming processors. Intel calls their implementation IA-32e instead.The Athlon 64 features an on-die memory controller and other major architectural enhancements giving it greater performance at the same clock speed as the previous Athlon and Athlon XP generation, even when running legacy 32-bit code. AMD has chosen to use a PR rating to designate the performance of these processors, supposedly relative to that of a hypothetically similar-clocked Athlon Thunderbird.
There are two variants: Athlon 64 and Athlon 64-FX. The Athlon 64-FX is similar to the Opteron and more powerful than the standard Athlon 64. Athlon 64 is able to run 32 bit, 16 bit, and AMD's own 64 bit assembly code. Currently, Linux, FreeBSD, and NetBSD support the 64-bit mode of Athlon 64, and Microsoft says it is developing a 64 bit version of Windows.
Athlon 64 also features CPU speed throttling technology branded Cool 'n' Quiet. When the user is running undemanding applications and the load on the processor is light, the processor's clock speed and voltage are reduced. This in turn reduces its peak power consumption from 89W to as low as 32W (C0 revision) or 22W (CQ revision).