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Anyone who follows the x86 CPU market over the past few years will have certainly heard of the now legendary codenames of “Hammer” and “SledgeHammer” (aka K8) used to denote the 64-bit x86 CPU ranges being developed by AMD. Whilst we first saw the “SledgeHammer” in the form of the Opteron range of server and workstation processors back in April, it is now time for AMD to unveil it’s range of desktop 64-bit CPUs in the range of Athlon 64 and Athlon FX processors. The release of both the Athlon 64 and Athlon FX CPUs is a significant event in that it marks the first extension of the x86 CPU away from being a 32-bit design. It is also significant in that traditionally it has been Intel which has previously extended the x86 CPU in this manner having moved from the original 8-bit 8086 design to 16-bit operation with the 286 in 1983 and from 16-bit to 32-bit operation with the 386 in 1985. Having seen many subsequent iterations of 32-bit processors since the 386, Intel saw the best way to develop a 64-bit CPU design was to abandon the ageing x86 architecture and to start afresh with the new IA-64 instruction set which forms the basis of the Itanium family of processors. The luxury of being able to invest upwards of $1 billion in an all new CPU architecture has never really been an option for AMD and the Athlon 64 line is a more pragmatic response to issues such as the 4GB limit of addressable memory which afflicts 32-bit CPU designs. The x86-64 design also follows the tradition of extending an existing architecture to accommodate new features and new design concepts. In many respects the AMD Athlon 64 and Athlon FX can be viewed as being the first affordable 64-bit CPUs as for the past 10 years this market has been dominated by the high-end server and workstation chips such as the Sun SPARC/Ultra SPARC, HP (nee Compaq & DEC) Alpha, HP PA-RISC and IBM Power series. If anything it is remarkable that it is an x86 based chip which has become the first affordable 64-bit CPU given the fact that it has been often predicted that the x86 instruction set would be eclipsed by the designs mentioned above. Interestingly AMD have seen fit to launch two separate chips into the desktop market in the form of the mainstream Athlon 64 and the high-end Athlon FX. This marks a change in strategy for AMD as it sees an overlap between the PC and the workstation market and can launch two separate parts (which will require different motherboards, memory types, and so forth).
This article will examine the design assumptions and enhancements behind the x86-64 design and how this fits into the x86 CPU hierarchy. It will also look at both of the Athlon 64 and Athlon
FX designs and how these compare to the Intel Pentium 4
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