Only half a dozen years ago, the computing world was abuzz over the seemingly limitless possibilities of the PC client/server networks that were popping up everywhere. As a result, computer-industry experts predicted the death of the mainframe computer was imminent. Just when it seemed that the "Big Iron" might find itself tossed into the scrap heap of history, the business computing landscape abruptly shifted. The emergence of the Internet and electronic commerce, the popularity of enterprise-resource-planning (ERP) software packages handling critical business transactions, and the creation of huge data warehouses all have spiked demand for computers that can handle high volumes of data efficiently, reliably, and economically. Toss in the fact that many IS managers are weary of maintaining vast numbers of distributed PCs, and the mainframe suddenly is attracting a second look. "Mainframes are making a genuine comeback," states Jeffrey Held, director of Ernst & Young's Center for Technology Enablement. "They are more sophisticated than they were a decade ago, and many organizations are now discovering that mainframes fit perfectly into today's high-transaction environments that require scalability and absolute reliability. PCs and UNIX servers have their place, but not in certain mission-critical areas." Gone are the monstrous water-cooled behemoths that once filled an entire floor and pulled enough power to require a small electrical generating plant. So are systems that offered nothing more than dumb terminals on the desktop and the ability to handle batch processing, such as payroll. "The technology has leaped ahead, and the cost has come down," says David Floyer, president of ImpactIT, a Mountain View, Calif., consulting company. "Today's mainframes offer capabilities that many companies truly need." Dataquest Inc., the market-research unit of Gartner Group Inc., estimates that worldwide vendor revenues for mainframes -- mostly manufactured by industry heavyweights IBM Corp., Amdahl Corp., Unisys Corp., and Hitachi Data Systems -- will drop from $14.1 billion in 1996 to $10.8 billion in 2000. But that's only part of the picture. Newer systems, based on the same CMOS (complementary metal-oxide semiconductor) technology that runs PCs, can process much higher workloads than their ancestors. In fact, during the last two years, processing power has shot up more than 400%. A decade ago, the typical mainframe cost nearly $80,000 per MIP (millions of instructions per second). Today's machines cost about $5,000 per MIP. "In many cases, the total cost of ownership for a mainframe is lower than other computing platforms," argues Floyer. He and other analysts say that the mainframe solves a very real problem. It allows companies to centralize data and IT operations, reduces the administrative hassle and cost of maintaining a highly distributed technology infrastructure, and provides a level of dependability that no other system -- including high-end UNIX servers -- can touch. With built-in operating systems and databases, there are simply fewer things to go wrong with mainframes. "Many companies have become dissatisfied with the highly distributed, unmanageable technology mess they have on their hands," says Held. "They're discovering that the mainframe environment can be managed, whereas PCs cannot." Although PCs have put enormous power on the desktop and are in no danger of disappearing, they fail miserably as mission-critical servers and repositories for data, Held argues. Whereas a PC can crash several times a day, a mainframe can go weeks or months without a single problem. Those who have stuck by mainframes all these years don't have to be convinced. "When it comes to UNIX, the tools just aren't there," says Janice Hardrath, director of IS at Aerostructures Corp., a $375 million (1997 revenues) Nashville manufacturer of aircraft assemblies and wings for commercial and military use. "We simply cannot have any kind of significant outage and continue to run the business. The entire manufacturing system is heavily dependent on computers." The company uses an IBM S/390 mainframe to manage manufacturing, finance, purchasing, and more. It recently installed ERP software from Baan Co. on the mainframe. At Lawson Products Inc., a Des Plaines, Ill., firm that distributes manufacturing products, including fasteners, specialty chemicals, welding rods and supplies, and hydraulic components, mainframes have always been part of the computing environment. However, in the early '90s, the firm began to migrate toward a more decentralized approach -- with mainframe computers at six distribution centers around the U.S. The systems dialed out to various local-area networks (LANs) and updated data once a day. More recently, Lawson reverted to a centralized mainframe setup, using a more powerful machine. The company has consolidated order entry, financials, billing, general ledger, inventory management, payroll, and other activities onto a single IBM OS/390. This machine handles all the processing for the firm's Baan ERP package and Lotus Notes groupware system. The mainframes at the distribution centers now act as servers managing local networks and uploading data to the central machine. Jim Mann, the company's CIO, describes the mainframe as "the heartbeat of our technology group." If needed, it also can run software with the UNIX operating system. When Mann examined the cost of handling everything under a true UNIX environment, he found that it would take between 24 to 30 server-level computers at a total cost that could exceed $3.5 million. Meanwhile, mainframe vendors are putting a new face on the venerable machine to attract new customers and retain companies that have always relied on the heavy metal. "One of the things that makes today's mainframes far more appealing," notes Ali Jenab, vice president of worldwide systems marketing for Sunnyvale, Calif.-based Amdahl, "is that they can run many of the same software packages as the PC. That allows companies to have the best of both worlds." SAP R/3, PeopleSoft, Baan, Oracle Financials, and Lotus Notes are just a few of the software applications packages that now can run on mainframes, and which can be harnessed as data servers in combination with business applications running on Windows NT or UNIX servers. "PCs and mainframes can now peacefully coexist in the same environment," says Ross Mauri, vice president of Systems 390 and hardware development for IBM. In their latest adaptation to the changing needs of business computing, mainframes are acting as Web servers. Companies managing huge amounts of data -- typically stored in a data warehouse -- are finding that a mainframe can speed processes throughout the organization. "Mainframes could be the killer application server of the future," says Ernst & Young's Held. Just as medical breakthroughs have added years to human life, technological advances have contributed to the mainframe's longevity. The footprint on Amdahl's 800 series mainframes is 43 sq ft, compared with 738 sq ft just three years ago. More important than improvement in size is the gain in computing power. Systems from the major mainframe manufacturers are approximately 10 times faster than their counterparts from 1990. Among other capabilities, these machines support UNIX, Java, the TCP/IP messaging protocol, and others, making it possible to connect the mainframe to LANs and WANs (wide-area networks). They also can be deployed as the backbone for corporate intranets and extranets. "The integration between various platforms is becoming seamless," says Jack Arnold, vice president of systems transition at AlliedSignal Inc., Morristown, N.J. With more than 70,000 employees, the industrial manufacturer has three mainframe computers running PeopleSoft's human-resources and payroll applications, Walker Corp.'s general-ledger system, an MRP package from Computer Associates, and assorted manufacturing systems. During the last three years, transaction volume on the mainframe has increased by about 10% annually. "Mainframes remain the best choice for handling high-transaction volumes across the company," Arnold says. But he believes high-end UNIX servers remain a viable alternative for the future. For instance, a new SAP R/3 installation will run on a Hewlett- Packard Co. (HP) server. The mainframe's resurgence notwithstanding, the rest of the computer industry isn't exactly standing still. Increasingly, NT and UNIX hardware makers, including Compaq Computer Corp., HP, Sun Microsystems Inc., Sequent Computer Systems Inc., and Data General Corp., to name a few, are adding features that blur the line between what once were distinct computing platforms. They're building servers with greater dependability, scalability and robustness. The upshot is that these machines are steadily encroaching on traditional mainframe territory. Sun's Starfire UE 10000 UNIX machine, for example, uses 64 Intel Corp. processors to handle high-end processing. It cannot run mainframe applications, but can handle leading ERP packages. Likewise, midrange computers such as the popular IBM AS/400 and HP 3000 come with an embedded operating system and database, just like a mainframe, but do not offer the upward scalability of a true mainframe. Admittedly, mainframes have problems of their own. They're not cheap, nor is the software that runs on them. And, Floyer argues, mainframe vendors haven't effectively marketed the machines as high-end Web servers. Clearly, though, like the cat that fell out of the third-story window and landed on its feet, the mainframe has earned itself another life. "Mainframes will be viable for years to come," says Amdahl's Jenab. "Each computing platform has its niche, and, ultimately, you have to choose the right tools for the job. In the future, the discussion isn't going to center on whether PCs, UNIX, or mainframes will win out in the marketplace. It will focus on how to integrate these three platforms together."