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An Apple MacBook Pro, a notebook often used as a desktop replacement.

A desktop replacement computer (dtr) is a personal computer that provides the full capabilities of a desktop computer while remaining portable. They are often a larger, bulkier laptop. Because of their increased size, this class of computer usually includes more powerful components and a larger display than generally used in smaller portable computers and can have a relatively limited battery capacity (or none at all). Some use a limited range of desktop components to provide better performance per dollar at the expense of battery life. These are sometimes called desknotes, a portmanteau of the words "desktop" and "notebook," though the term is also applied to desktop replacement computers in general.^[1]

The forerunners of the desktop replacement were the portable computers of the early-to-mid 1980s, such as the Osborne I, ^[2] the Compaq Portable ^[3] and the Commodore Executive 64 (SX-64) computers. ^[4] These computers contained the CPU, display, floppy disk drive and power supply all in a single briefcase-like enclosure. Similar in performance to the desktop computers of the era, they were easily transported and came with an attached keyboard that doubled as a protective cover when not in use. They could be used wherever space and an electrical outlet were available, as they had no battery.

The development of the modern desktop replacement computer came with the realization that many laptops were used in a semi-permanent location, often remaining connected to an external power source at all times. This suggested that a market existed for a laptop-style computer that would take advantage of the user's reduced need for portability, allowing for higher-performance components, greater expandability, and higher-quality displays.

Modern desktop replacements generally perform better than traditional laptop-style computers as their size allows the inclusion of more powerful components. The larger body means more efficient heat-dissipation, allowing manufacturers to use components that would otherwise overheat during normal use. Furthermore, their increased size allows for greater expandability and features, as well as larger and brighter displays. However, these advantages generally come at a price premium, with many computers in this class costing as much as two desktop computers with similar specifications.

Using a laptop form factor, however, desktop replacements still often suffer from limitations similar to those of more mobile laptops. They usually lack the ability to accept standard PCI expansion cards, limiting their usefulness somewhat. While the computers can offer slightly better cooling than other laptops, they rarely dissipate heat efficiently enough to allow for high-end desktop-class components, and thus may not reach the same performance levels as desktop computers.

Desktop replacement computers are, with a few exceptions, difficult to upgrade compared to desktop computers, with many of their major components (such as the display) integral to the design of the machine, and others (such as the CPU and GPU) often being hard to access and replace.^[5] A small segment of desktop replacements do not include a battery as a standard feature, while some do not include PC-Card support. They have the same limitations on serviceability as laptops, and can rarely use identical components to a desktop computer.