ATLANTA -- In the spring of 1863, only two armies were vexing Atlanta in what some people here still call the War of Northern Aggression. Last week, three armies were challenging the city's hospitality during the Comdex/Spring computer trade show: Microsoft unfurled its Windows NT battle flags, IBM sent in reinforcements for its OS/2 software, and the grizzled veterans of Unix found some fresh horses to ride.
The combativeness was just one more sign that the personal computer industry is at a crossroads. Microsoft, through DOS and Windows, clearly owns the office desktop today, but despite Windows' huge popularity, the program was designed to run on microprocessors that virtually nobody uses anymore.
Windows does not take advantage of 32-bit microprocessors, which include Intel Corp.'s i386DX and i486DX chips, the workhorses of the typical office. So many corporate information system managers are trying to decide which advanced operating system should be the platform on which to carry their PC operations into the 21st century.
Unlike the Civil War, this battle is unlikely to result in an unconditional winner. As businesses transform their large, centralized information systems into smaller systems of personal computers linked on networks, there may well be room for several different systems within one company.
As a result, many companies are flying the colors of more than one advanced operating system, prepared to embrace whichever one -- Windows NT, OS/2, Unix or some other system not yet visible -- eventually gains the strongest position.
"We love them all equally and hate them all equivalently," said Jim P. Manzi, chairman of Lotus Development Corp., which is developing programs for all the platforms. "Our strategy is operating system agnosticism."
Such agnosticism is not possible for the people who have to decidecorporate computing strategies. In coming months, if they have not done so already, many corporate managers will be evaluating Windows NT, OS/2 version 2.1 and probably some of the Unix variations.
These include Solaris for X86, from Sunsoft Inc.; Nextstep for Intel from Next Inc.; Unixware from Univel, and Open Desktop from the Santa Cruz Operation -- for use on the powerful PCs called servers that act as hubs and information repositories for other personal computers on the network.
Some desktop PC users, typically the breed who think of themselves as "power users," will be pouncing on the new operating systems in an effort to wring the maximum performance from their machines. Almost every company has a few of these wise guys, who demand the fastest and brawniest PCs. For these users, the queries for a good operating system will be:
* Will it be solid and reliable enough to entrust it with the most important applications?
* Does it have the proper plumbing for use on networks, including security features?
* Does it have the ability to run on a variety of powerful computers, including future generations of microprocessors and computers with multiple processors? Such portability, as it is known, provides users enormous flexibility in choosing hardware.
Other questions include: Will it have a rich set of development tools for people who create applications? Will it have sufficient support among commercial software writers?
If the new operating system is to run on desktop PCs as well as on the more powerful systems called workstations and servers, how much memory and processing power will be needed?
Not for casual users
It wasn't long ago that people made fun of IBM's OS/2 because it required eight megabytes of system memory and 40 megabytes of hard disk space. Some analysts expect that Windows NT and the Unix variants will demand 12 to 16 megabytes of system memory and 50 to 100 megabytes of hard disk space before they will do any useful work. Clearly, with the possible exception of OS/2, these are not operating systems for the casual user.
That group -- the office workers and the executives who are happy with a simple desktop PC or portable computer -- are the civilian noncombatants in this conflict. They may be aware of distant thunder, an occasional bright flash and lots of smoke, but the 32-bit systems have no real impact yet on day-to-day life.
With apologies to "Gone With the Wind," the attitudes of most casual PC users to these ominous activities beyond the horizon seem to range from disassociation ("Fiddle-dee-dee, I'll worry about that tomorrow") to cynicism ("Frankly, my dear, I don't give a damn").
But it does matter.
The last major operating system crossroads was passed more than a decade ago when eight-bit personal computers using the CP/M operating system gave way to 16-bit computers running DOS and, more recently, Windows. And the time has now come for those 16-bit systems to give way to an operating system that issues instructions 32 bits at a time.
The microprocessors needed to handle 32-bit instructions have been around for years, first in the rarefied Unix world and later with Intel's 386DX chip. But PC users have not been able to tap into the microprocessor's 32-bit power without risking compatibility with all the 16-bit DOS software already on the market. And most office workers, particularly those who work with word processing and simple spreadsheets, are a long way from exhausting the potential of DOS, Windows or the Macintosh. Even so, there is a lot to gain from 32-bit power.
"It will make everything much faster in the future," said Jeffrey Henning, senior industry analyst with BIS Strategic Resources of Norwell, Mass. "The computers will be able to do more. It will make themeven easier to use."
So if 32-bit computing is so great, why haven't businesses embraced Unix, which has been around for 20 years?
For many, many years we've heard the Unix technocrats saying, 'This will be the year of Unix,' and expecting people to demand 32-bit capabilities," said Richard Dionne-Keay, an industry analyst with Summit Strategies, a consulting company in Boston. "Unfortunately, Unix had too many liabilities hampering its 32-bit performance. Once they finally get a 32-bit operating system with a lot of applications on the desktop, the performance should improve."
Among the Unixes, the most impressive is Nextstep for Intel, introduced this month. "It's the best operating system out there, certainly the technology leader," said Philippe Kahn, chief executive of Borland International Inc., a software maker. "But I don't think it has a chance to be a market leader."
Kahn said he runs Nextstep on a machine with 32 megabytes of system memory, hardly the typical configuration.
For many people, IBM's OS/2 version 2.1 may be the best choice. It offers strong server abilities, along with a Macintosh-like user interface, and it can run DOS and Windows programs.
The power of Microsoft, and the momentum of Windows, makes Windows NT an early favorite, even though it is not yet available to the general public. Most versions of NT will be available by August.
When he announced Windows NT in a speech here last week, Bill Gates of Microsoft said he expected to sell a million copies within a year. Surely he could sell millions of copies if he lowered the price to $99, or even $49, as IBM has done with OS/2. As it is, many people will be able to buy the desktop version of NT for $150 or less. And even at that price, many power users will find it irresistible and get it on their own, company policy notwithstanding.
"It's no problem to bury the cost in a couple of expense reports," noted Bernd K. Harzog, program director for personal computing for the Gartner Group in Stamford, Conn.
Only half-jokingly, he suggested that Microsoft was clever in giving Windows NT the same screen design as Windows 3.1, even though they differ significantly under the hood. "A power user can install it and have it running on his machine, and when the system administrator comes by, it looks just like Windows," he said.
(Peter Lewis works out of the New York Times' Austin, Texas, bureau:  328-8258.)