Machines that follow a formula like Intels slim desktop are likely to be the most popular because they will use standard components, which keep costs low, but still offer the benefits of smaller size, observers say.
Ultrasmall form factor machines, on the other hand, are likely to cost more, as they tend to use pricier notebook parts.
Given that notebook PCs are expected to start out-shipping desktops in the United States later in this decade, that means the market for desktops is shrinking, IDCs Shim said. However, desktops themselves—and even minitowers—wont completely disappear.
Many buyers are still concerned about costs or harnessing the largest possible amounts of computing power, two things that will allow desktops to continue to find favor for the foreseeable future, particularly in corporate workstations and in gaming desktops.
Game machines and workstations are typically made larger to accommodate higher-performing processors—which generally produce more heat, something thats difficult to evacuate from smaller confines—as well as extra components, including up to four hard drives, sound cards and bleeding-edge graphics cards (which also now produce relatively large amounts of heat).
Small form factor machines generally provide space for an optical drive, at least one hard drive and an add-in card. But towers and minitowers usually offer several extra bays and slots for drives and add-in cards, making them more attractive for some applications.
Over time, the same trends toward small desktops will occur globally, IDC predicted, as the PC market will continue to grow by at least high-single-digit numbers. However, the shift will occur more slowly, Shim said, as some markets will adopt the lowest-possible-cost desktops.
Minitowers, which accounted for 93 million units or almost 70 percent of desktop shipments in 2005, are expected to drop to 78 million units in 2009, less than half of desktop shipments expected that year.
During the same period, 2005 to 2009, small form factor machines will rise from about 12 million units, or roughly 9 percent of shipments, to about 48 million units, about 30 percent of desktop shipments, IDC predicted.
"The small form factor [desktop] will help legitimize other smaller form factors, driving the miniaturization of components, make smaller parts more common and therefore cheaper as [the small desktop] goes from a specialty product to a more mainstream product," Shim said.
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