The 64-bit x86 architectures from Advanced Micro Devices Inc. and Intel Corp. are nearly identical, according to an independent analysis by In-Stat/MDR's Microprocessor Report.

Nearly 100 percent software compatibility is possible, but in some cases programs written for one 64-bit architecture may not run properly on the other 64-bit architecture, the report said.

The study compared all the new instructions, modified instructions, deleted instructions, and modifications to the register files, including control registers, system registers, and registers visible to application programs.

Memory-addressing schemes and many other architectural features, such as data-addressing modes, context-switching behavior, interrupt handling, and support for existing 16-bit and 32-bit x86 execution modes were also compared. In every case, Intel had patterned its 64-bit x86 architecture after AMD64 in almost every detail, the researchers concluded.

However, the Microprocessor report discovered a few differences that even Sunnyvale, Calif.-based AMD and Intel were unaware of, according to In-Stat/MDR. Some of these differences may be resolved in future 64-bit x86 processors. In other cases, software can easily adapt to the differences by executing slightly different code, after first probing the CPU to learn which 64-bit extensions it supports.

Despite the differences, the researchers concluded Intel "clearly derived" its 64-bit architecture by reading AMD's prerelease documentation for AMD64 and by testing AMD64 processors.

By: DocMemory
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