Everybody goes MMX - and x86 compatibility takes a hit

Intel's MMX technology may have opened Pandora's box. Four CPU vendors will offer additions to the MMX instruction-set extensions in 1998, but as these companies go off in different directions, compatibility is at stake. While Intel works on additions to the MMX instruction set, dubbed MMX2 by analysts, its competitors Advanced Micro Devices, Centaur, and Cyrix have in the same week each described their own MMX enhancements for multimedia.

Four CPU vendors will offer additions to the MMX instruction-set extensions in 1998, but as these companies go off in different directions, compatibility is at stake.

"The x86 instruction-set architecture is beginning to fragment," says Michael Slater, principal analyst at MicroDesign Resources, in Sebastopol, California.

Intel is said to be working on additions to the MMX instruction set, dubbed MMX2 by analysts. Advanced Micro Devices, Centaur, and Cyrix this week each described its own MMX enhancements for multimedia.

Analysts questioned how different instruction sets would impact users. Major problems could arise if programs written for one instruction set won't run, won't run properly, or will crash a system using a CPU with a different architecture.

The chip suppliers will likely work out their differences to avoid these uncertainties, says Dean McCarron, an analyst at Mercury Research, in Arizona.

"We are committed to working much more closely with Cyrix and Centaur, and even Intel," agrees Atiq Raza, senior vice president and chief technical officer at AMD.

In the first half of 1998, AMD will introduce the K6 3D processor, code-named Chompers, at 300 MHz moving to 350 MHz, according to Jerry Sanders, AMD board chair and chief executive. The chip, now in limited availability, will use new instructions supported by Microsoft DirectX, he noted.

Later in 1998, AMD plans to release the K6+ 3D processor, with clock speeds as fast as 400 MHz, Sanders says. This chip will add a backside Level 2 cache running at the full speed of the processor.

Cyrix will enhance its 6x86MX processor in the second half of 1998 with its Cayenne CPU core, says Robert Maher, vice president of engineering at Cyrix. The core will offer performance equivalent to 300-MHz to 400-MHz CPUs, he says.

Centaur, too, will aim at graphics applications with its C6+ Pentium MMX-level CPU. Set for limited availability early in 1998 and volume before midyear, the C6+ will add 26 instructions to process Microsoft DirectX calls in hardware, says Jamal Haider, director of marketing at Centaur, in San Jose, California.

Advanced Micro Devices Inc., in Sunnyvale, California, is at http://www.amd.com/. Centaur Technology Inc., in Austin, Texas, is at http://www.winchip.com/. Cyrix Corp., in Richardson, Texas, is at http://www.cyrix.com/. Intel Corp., in Santa Clara, California, is at http://www.intel.com/.

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