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What exactly is a thin client?

Although NCs, Windows Terminals, and Net PCs are more or less aimed at the same market, the three different "thin client" products vary widely.

Michael Kanellos Staff Writer, CNET News.com
Michael Kanellos is editor at large at CNET News.com, where he covers hardware, research and development, start-ups and the tech industry overseas.
Michael Kanellos
4 min read
Although NCs, Windows Terminals, and Net PCs are more or less aimed at the same market, the three different "thin client" products vary widely in performance and capability, a three-way split that in turn dictates different back-end capabilities for each architecture.

Windows-based terminals: Windows-based terminals (WBTs) are primarily distinguished by the software that runs them, according to Mark Templeton, vice president of marketing at Citrix.

Under a WBT system, the desktop exists only as a window to the server. All data storage, application storage, and all of the significant computing functions take place on the server. The Citrix WinFrame system functions as the communication blanket that allows the server and client to interact. Technically, WinFrame consists of three parts: client software, server software, and a network protocol.

Microsoft's Hydra software functions in roughly the same manner and is based partly on Citrix's technology. Hydra clients also include Windows CE-based handheld devices. Both Hydra and Citrix run on top of Windows NT.

Hardware specifications for clients remain fairly low. WBTs need only 4MB or more of memory and can run on last-generation 486 processors. Hard drives are not needed. Users can also adopt old Macintosh or Windows computers as WBTs.

The lightness of the client, however, creates a need to build up the server's capabilities, according to Microsoft's John Frederiksen, group product manager for Hydra. Each client gets its own file on the server. Hence servers have to be fairly powerful. Further, only a limited number of persons can run applications at one time. Citrix's basic version of WinFrame accommodates 15 users but can be expanded.

The problem becomes especially acute if users want to employ these devices as desktop computers. "You can get up to 200 users on certain business line application. But if there are 15 other people on the network, and I decide to load a spreadsheet, there are problems," he said.

Technically, WBTs have not been released because no current terminals exactly meet Microsoft's specification, Frederiksen said. Templeton and others, however, assert that terminals from Boundless, Wyse, and NCD running WinFrame qualify as WBTs.

Network computers: A network computer is essentially a WBT with increased processing power that is based typically around Java rather than the Windows NT operating system.

"The difference between the NC and the Windows-based Terminal is the Java slant," said Eileen O'Brien, an analyst at International Data Corporation. NCs can connect to a virtually all back-end server platforms. WBTs must run on top of Windows NT, she said.

NCs, however, often require a Java Virtual Machine (a client-side software layer) to operate and typically run Java-based applications. Sources who have seen demonstrations of NCs report that the JVM and applications designed for the NC run slowly.

Interoperability is also far from perfect. NC backers are meeting in January to hammer out standards that will allow boxes from different makers to communicate readily with different servers.

Despite the publicity surrounding Java in the past year, corporate America remains skittish on moving to the new platform.

"Java could be the best, but it is an unknown," Ahmad Gramian, principal at CorpInfo Systems, a Los Angeles integrator, told CNET recently. "Typically, customers are pragmatists. They like to follow."

Although NCs can accommodate hard disks in certain configurations, they generally share applications and store data on the server. They do, however, perform computing tasks locally.

While Sun Microsystems and Oracle first touted the NC as a complete computing device, these companies concede that it will be marketed at least for now as a terminal replacement. Most beta sites for Sun's Javastation, in fact, have used the machines for dedicated purposes.

Javastations have been released to only a limited number customers. A more general release is expected later this year. IBM is the largest vendor to come out with a commercial release. Recently, the company reported that American Eagle had installed 365 IBM Network Stations.

Net PCs: These are generally the easiest of the thin clients to grasp conceptually. In a nutshell, Net PCs are ordinary PCs that conform to the "manageability" standards enunciated earlier this year by Intel, Microsoft, Dell Computer, and others. The standards suggest that the Net PC not include a floppy drive and that the machine conform to the Desktop Management Initiative (DMI), which allows managers to shut down, turn on, and generally control these machines remotely.

Unlike WBTs and most NCs, Net PCs contain a hard drive and can operate even if the network is down.

Although versatile, the market for these machines has eroded since being launching in June, primarily because the PC manufacturers have taken the best features of the Net PC and incorporated them into their mainstream PCs, according to Roger Kay, computer analyst at IDC. Personal computers have also dropped substantially in price, making the "sealed case" option less attractive.

IBM canceled plans for a Net PC earlier this year. Compaq Computer, Hewlett-Packard, and others, however, started releasing Net PCs in late September.  

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