Hyper-threading, announced in August 2001, is Intel's take on simultaneous multithreading, a microprocessor design concept that essentially makes a chip behave more efficiently. With threading, different regions inside the processor, such as the floating-point unit for decimal math and the integer unit, can process different applications, or application threads, at the same time. In contrast, most current processors behave like a wood chipper, processing threads in a fairly linear fashion. Therefore, many of the traditional processor's resources remain dormant while others work. When the technology was announced, Intel said that a workstation with hyper-threaded Xeon chips running Alias-Wavefront, a graphics application, achieved a 30 percent improvement in tests. To operating systems and applications, chips with hyper-threading look like two chips, and that's where the hitch lies. Software needs to be broken into threads before it can run on two chips simultaneously. In the server market, applications and operating systems have already been threaded. In workstations, the practice isn't as prevalent, said an HP representative. As a result, the function is turned off in the company's X4000 workstation. HP in the coming weeks plans to come out with a new line of Windows 2000 and Windows XP workstations, but hyper-threading won't be available. An HP representative said most of the applications for workstations, predominately tailored for Windows 2000, don't take advantage of the technology. A Dell representative echoed the sentiment. "In workstations, hyper-threading remains application-dependent," said the representative, who added that Dell's Precision 530 workstation comes with the hyper-threading function turned off. Both HP and Dell, though, make the technology easy to turn on. With upcoming desktops, the situation will be reversed. Windows XP has been optimised for the technology and so have many applications. Performance gains will be the largest when the application is also threaded (as well as optimised specifically for hyper-threading), but gains will still occur on unvarnished applications, said Dean McCarron, an analyst at Mercury Research. "I'm fully expecting at least a modest improvement" in most situations, McCarron said. Still, Glaskowsky said problems could occur with single-threaded applications even on a multithreaded operating system. If the processor is running two threads, the chip has to split its cache -- a reservoir of memory located on the processor -- and other shared resources. Historical examples have shown that regular software that's run on computers with two chips runs worse than on single-processor boxes. "You need something that was designed to run on two processors," said Glaskowsky. Otherwise, "it adds a dose of dissatisfaction."
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