If two heads are better than one, why not a dozen? Or 50, or 100? That's the latest thinking in the commercial data processing market. For 40 years, mainframers such as IBM and Unisys have struggled to build the fastest single computer possible. But now they're bumping into fundamental physical limits, making each new speedup terribly expensive. So, the commercial mainframe industry, like supercomputer makers before it, is turning to parallel processing, ganging together scores of cheap microprocessors to attack big computing problems en masse.

On Aug. 3, Unisys Corp. and Intel Corp. jumped into the game. They're teaming up to build a commercial "mainframe" based on Intel's high-powered Pentium microprocessor. Neither prices nor details were announced, and shipments won't begin before 1995, officials said. But the deal makes this clear: The traditional mainframe's days are numbered. Parallel designs can do more work than traditional ones (chart) and for far less money. Unisys and Intel join AT&T's NCR unit, IBM, Sequent Computer Systems, Pyramid Technology, and some small supercomputer companies in the rush to exploit parallel computing. "It's quite clear that harnessing microprocessors together is the way to go," says Peter Kastner, vice-president of consultants Aberdeen Group Inc.

Leading the pack has been AT&T/NCR, with more than 300 parallel systems installed among more than 150 customers worldwide. Most of those are add-ons to IBM mainframes that help crunch through massive data bases. But NCR also has begun shipping a general-purpose version, the 3600, that it markets as an alternative to standard mainframes.

BIG BLUE LINE. But the pressure on NCR is mounting: Mainframe leader IBM is preparing to go parallel, too. Formally, all Big Blue has introduced is a parallel computer designed mainly for scientific use, the SP1. IBM has focused on the scientific market because it wants to keep selling standard mainframe gear. But IBM says it will ship a parallel-processing add-on for its System/390 mainframes by 1994. And in June, it hired Ben C. Barnes, a former NCR large-systems executive, to exploit the SP1.

Intel, whose processors NCR uses across its entire product line, is entering the fray, too. A leader in scientific parallel computers, Intel is sharing with Unisys its expertise in creating efficient meshes, or high-speed networks, to connect hundreds of processors in a single machine. Unisys, No.2 in mainframes, will contribute its understanding of commercial customers' needs. Still, William J. Eisenman, vice-president of NCR's Large Computer Products Div., isn't worried. He reckons NCR can stay years ahead of Intel and Unisys--and IBM--in parallel-ready software.

Conventional wisdom has it that the PC revolution is all but killng off the mainframe. But if the mounting rage for building alternative "mainframes" is any indication, the high end of the computer market has life in it yet.

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