Disk Advances Open Unlimited Horizons

COMPUTER users don't think about their hard disk. It stores their data, makes that whirring noise, and remains as mysterious and sealed up as any part of the machine.

But that disk is the heart of your computer. If the machine vanished tomorrow, you could replace every component except the data that sit on your spinning disk.

This column isn't about backing up your data (although that is very important). It's about technological advances in a single part of a complex machine that change the way we use the machine. A nearly 40-year-old revolution in disk technology has brought us to the present. I think another big change is around the corner.

Before IBM launched the first commercial hard disk in 1956, computers were different machines. Data resided on cards or computer tapes. To get to the data, you had to process the computer cards or the tapes.

IBM's 305 Ramac changed all that. It held 5 million characters of data. (Five megabytes. Imagine that!) More important, it allowed users to access computer data directly without going through a batch process. Bill Nelson of IBM's hard disk unit, Addstar, calls it probably the most important computer development of the decade.

"It took us from the business of being a back-office batch-processing machine to being an on-line interactive business tool," he says.

The Ramac was a monster. It stood six feet high and four feet wide - an overlarge refrigerator stuffed with 50 spinning platters, each one 24 inches in diameter.

Skip forward to 1993. In March, IBM announced a new disk drive based on the idea of the Ramac but far, far smaller (3-1/2 inches wide and 1 inch high). It can carry 1 billion bytes (one gigabyte). Just under nine Ramacs can now fit on one square inch of IBM's new drive.

Over several decades, the capacity of hard drives has gone up an average 30 percent a year, says Jim Porter, president of a Mountain View, Calif., market research firm called Disk/Trend. In the last two years, capacity has grown at 60 percent a year, thanks to some new technologies and the increasing demands of sophisticated software. Today's average personal computer now holds 120 megabytes - about the capacity of a typical IBM mainframe in the mid-1960s. If the recent growth rate continues, the capaci ty of the average desktop will reach around 3 gigabytes by the end of the decade.

And disks keep getting smaller, too. Hewlett-Packard has a new drive that's only 1.3 inches wide.

It's this twin push - smaller and higher-capacity hard drives - that's nudging us into a new era of anywhere/anytime computing. Portable computing depends on a lot of advances. But if hard drives were still the size of refrigerators, portable computing wouldn't exist.

Disk companies sound confident that they can keep up the pace with new breakthroughs.

Seagate, the world's largest hard-drive company, is one of many examples. It has started using a new glass-ceramic product from Corning as the basis (or substrate) for some of its drives. Because the new product can be polished more finely than aluminum, the traditional substrate, Seagate says it will be able to reduce the distance between the disk and the recording head from 3 millionths of an inch to 2 millionths or, maybe, 1.5 millionths of an inch. That, in turn, would allow the disk to pack more inf ormation - up to 25 percent more.

Such improvements aren't trivial. Imagine driving down the highway at 250 miles an hour and keeping a tiny recording head less than a hair's thickness away from your spinning car wheel. Those are the tolerances these companies are working with.

Sort of makes your hard drive sound pretty fragile, doesn't it? But don't worry. Somehow, the scientists also keep coming up with ways to make hard disks more reliable. IBM's new one-gigabyte drive isn't expected to fail for an average 800,000 hours.

That's 91 years and four months of nonstop computer use.

* Send your comments on this column to CompuServe (70541,3654) or Prodigy (BXGN44A).

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