Advanced Micro Devices Inc unveiled its plans to challenge Intel Corp’s IA-64 architecture (aka Itanium) at the Microprocessor Forum yesterday, with an extension of the current x86 architecture to 64-bits. Sledgehammer, the codename for AMD’s K8, will incorporate both the new architecture and a high-speed system bus AMD is calling Lightning Data Transport. The move plunges AMD into uncharted territory – Intel non-compatibility. But AMD claims its strategy will offer users the option of a simpler upgrade to 64-bits which maintains compatibility with the existing x86 32-bit installed base of applications and operating systems.
AMD plans to extend the x86 instruction set to include a 64-bit mode, said Fred Weber, AMD’s vice president of engineering. The 64-bit mode has both a 64-bit address space and a 64-bit data space. Future 64-bit processors will be able to detect which mode is needed (32- or 64-bit) and compute accordingly. No other 64- bit solution has full native x86 32- and 64-bit compatibility” said Weber. The introduction of Sledgehammer would enable AMD to offer a leading-edge performance roadmap for the existing installed base he said. AMD said it has disclosed specifications to Microsoft Corp and the other operating systems vendors so that their system software and tools can be made x86 64-bit aware.
Intel counters that IA-64 has full i32-bit compatibility in the hardware for direct execution, and says that the systems functions of 32-bit programs running on Itanium will have their systems functions automatically carried out in 64-bit mode for full native performance. It’s no secret, however, that Intel intends to keep up parallel development of its 32-bit line of processors until well after the second generation IA-64, McKinley, makes it to market. Intel has also indicated that it doesn’t expect there to be a huge volume 64-bit business until the McKinley timeframe, a year on from Itanium.
AMD will now pitch Sledgehammer as the only 64-bit, x86- compatible alternative to IA-64. MIS managers [can] continue using a tested and preferred instruction set, without having to choose one instruction set over another, or sacrifice current investments in 32-bit applications and operating systems the company said in a statement. It should also be an easier target for compiler writers and an easier port for systems software vendors. It’s a move reminiscent of previous attempts to move beyond the PC architecture, either by extension or replacement. Way back in 1987, Compaq Computer Corp dueled with IBM Corp over the replacement for the standard PC ISA hardware bus, with Compaq proposing the compatible EISA extensions against IBM’s proposed clean-sheet replacement, the MCA Micro Channel Architecture bus. EISA was the eventual winner.
The new system bus, Lightning Data Transport, will offer a 20 times increase in bandwidth for I/O, co-processing and multi- processing functions, improving overall systems performance, said AMD. LDT can achieve a bandwidth of up to 6.4 Gbps per connection, compared to today’s best of 266 Mbps. It will work with externally visible bus standards such as PCI or SIO, providing fast connections to both. A two-way chipset and bridge chips are planned for the second half of 2000, incorporating the LDT interconnect. AMD is expected to report its third-quarter figures today.
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