Inpersonal computing, atower unit, or simply atower, is aform factor ofdesktopcomputer case whose height is much greater than its width, thus having the appearance of an upstandingtower block, as opposed to a traditional "pizza box" computer case whose width is greater than its height and appears lying flat.
Compared to a pizza box case, the tower tends to be larger and offers more potential for internal volume for the same desk area occupied, and therefore allows morehardware installation and theoretically betterairflow forcooling. Multiple size subclasses of the tower form factor have been established to differentiate their varying sizes, includingfull-tower,mid-tower,midi-tower,mini-tower, anddeskside; these classifications are however nebulously defined and inconsistently applied by different manufacturers.
Although the traditional layout for a tower system is to have the case placed on top of the desk alongside themonitor and otherperipherals, a far more common configuration is to place the case on the floor below the desk or in an under-desk compartment, in order to free up desktop space for other items.[1] Computer systems housed in the horizontal "pizza box" form factor—once popularized by theIBM PC in the 1980s but fallen out of mass use since the late 1990s—have been given the termdesktops to contrast them withtowers that are often situated under the desk.
Tower cases are often categorized asmini-tower,midi-tower,mid-tower,full-tower, anddeskside. The terms are subjective and inconsistently defined by different manufacturers.[2][3][4]
Full-tower cases, typically 20 inches (51 cm) or more in height, are designed for maximum scalability.[5] Forcase moddingenthusiasts andgamers wanting to play the most technically challengingvideo games, the full-tower case also makes for an idealgaming PC case because of their ability to accommodate extensivewater cooling setups and largercase fans.[6] Traditionally, full-tower systems had between four and six externally accessible half-height5.25-inch drive bays and up to ten3.5-inch drive bays.[6][5]: 138 Some full-tower cases included locking side-doors and other physical security features to prevent theft of the discs inside those bays.[7] However, as modern computing technology has moved away from mechanicalhard drives andoptical drives towardsolid-state devices such asUSB flash drives,solid-state drives (SSDs), large-capacityexternal storage, andcloud storage, such an abundance of internal and externaldrive bays is less common.[8][9] More recent full-tower cases instead only have one or two external drive bays, or none at all, with the internal bays moved elsewhere in the case to free up room and improve airflow.[10]
Full-tower cases readily fit full-sizeATXmotherboards but may also accommodate smallermicroATX motherboards due to the former standard's interoperability in mounting holes. Full-tower cases may also have increased dimensional depth and length over their shorter counterparts, allowing them to accommodateExtended ATX motherboards, largergraphics cards andheat sinks.[10] Since the 2010s, full-tower cases are commonly used by enthusiasts as showpiece cases with custom water cooling,RGB LED lighting, andtempered glass oracrylics side panel.[11][12][13] They may also hold two motherboards (as is the case with theCorsair 1000D) and dual power supplies (Corsair 900D).[14][15]
Mid-tower cases, usually between 16 inches (41 cm) and 20 inches (51 cm) in height, are the most common form factor ofpersonal computer towers.[6][10][16] Before the late 2010s, mid-towers contained between three and four 5.25-inch drive bays and an equivalent number of 3.5-inch bays to houseoptical disc drives,floppy disk drives andhard disk drives, leaving just enough room for a standard ATX motherboard andpower supply unit.[16] Since the widespread adoption ofUSB flash drives,solid-state drives (which take up far less space than spinning hard disk drives) and the declining usage of internal optical drives, the number of drive bays has become less of a concern to the contemporary computer user, the internal space of mid-towers is now used more commonly for closed-loopwater coolers, dualgraphics cards, and tightly stacked SSDs.[10]
The marketing termmidi-tower sometimes refers to cases smaller than a mid-tower but still larger than a mini-tower (seebelow), typically with two to three external bays.[17] Other times the term may be synonymous withmid-tower.[18]
Mini-tower cases, between 12 inches (30 cm) and 16 inches (41 cm) in height,[19] slot between theMini-ITX specification forsmall-form-factor PCs and the archetypal mid-tower. Mini-towers typically will only accommodatemicroATX motherboards and for this reason sell in fewer numbers in the consumer market than the other size classes of computer towers.[10][20]: 94–95 Traditionally, mini-towers had only one or two disk drive bays (either 5.25-inch or 3.5-inch).[21]
The termdeskside is primarily a term of art in theworkstation market, referring to computer towers with a much wider footprint than traditional domestic tower units. These wider deskside cases accommodate a far greater amount ofcentral processing units (CPUs), drive bays, memory slots,expansion slots,peripherals, andI/O adapters, among other devices.[4][22]: 20 [23]: 57
The tower form factor may be seen as a proportional miniaturization ofmainframe computers andminicomputers, some of which comprise massive tall enclosures standing almost to the ceiling.[24] In the advent of themicrocomputer era, most systems were configured with thekeyboard built into the same chassis that the main systemcircuit board resides. Such computers were also termedhome computers and counted such popular systems as theApple II,TRS-80,VIC-20, andCommodore 64, among others. In 1981, IBM introduced theIBM Personal Computer, a system which was met widespread adoption in both enterprises and home businesses within a couple years and set a newde facto standard for the physical configuration of microcomputers. The IBM PC and successors housed the system board andexpansion cards in a separate horizontal unit, with the keyboard usually in front and the prescribedCRT monitor resting on top of the system unit; the front of the system unit houses one or more disk drives.[25]
In 1982,NCR introduced the Tower series ofworkstation computers, named so for their tall, upright configuration, intended to be stowed away under a desk. The first, the Tower 1632, is 29 inches tall and featured aMotorola 68000 microprocessor. Costing upwards of $12,500, the 1632 is meant to runUnix and supports up to 16 simultaneous networked users.[26] NCR continued adding to the Tower line into the late 1980s.[27][28][29]
In 1983,Tandy Corporation offered theirTandy 2000 with an optional floor stand, turning the normally horizontal desktop case on its side and allowing it to be stashed under-desk; the square badge on the Tandy 2000 can be removed and rotated upright in turn.[30] IBM followed suit with theirPC/AT in 1984, which included an optional "floor-standing enclosure" for $165.[31] Of the three initial entrants in the company'sRT PC line in 1986, two were tower units, while the other was a traditional horizontal case like the AT and the PCs before it.[32]
In 1987, IBM introduced thePS/2 Model 60, an initial entry in the company'sPersonal System/2 line of personal computers. It was IBM's first Intel-based PC built entirely into a tower case.[33] The PS/2 Model 60 was comparable in technical specification to its sibling thePS/2 Model 50, which sported a horizontal desktop form factor. Whereas the Model 50 had only four expansion slots and three drive bays, however, the Model 60 featured eight expansion slots and four drive bays. Because of the latter's increased potential for connectivity and multitasking, technology journalists envisioned the PS/2 Model 60 as a multiuser machine, although multiuser operating systems supporting the80286 processor of both the Models 50 and 60 were hard to come by in 1987.[34] IBM followed up with the tower-basedPS/2 Model 80 later that year, their first PC powered by ani386 processor.[35]
According toThe New York Times in 1988, the PS/2 Models 60 and 80 started the trend of computer manufacturers offeringIBM PC compatibles in optional tower form factors:
A countertrend is to take PCs off the desk and put them on the floor. IBM started it with the tower configuration for its PS/2 Models 60 and 80, and at least a dozen companies were showing floor-standing PCs atComdex. Freed from the need to fit on a desk, some of the tower models are actually getting bigger to accommodate large disk drives, a variety of floppy drives and backup devices, and room for up to a dozen slots for plug-in boards.[36]
Aftermarket floor stands, allowing existing horizontal desktop computers to be stored upright on the floor, were sold in the late 1980s by companies such asCurtis Computer Products.[37] Recommending such kits inThe Washington Post in 1989, Brit Hume called the tower the best configuration for ergonomics and noted that, "Contrary to popular myth, standing vertically will not hurt the computer or throw off your disk drives."[37]
The transition in dominance from horizontal desktop computers to towers was mostly complete by 1994, according to a period article inPC Week.[38] Computer cases or pre-built systems offered in the traditional horizontal form factor have since been separately categorized asdesktops, to contrast them with the usually-floor-situated towers.[21]
Brian Benchoff ofHackaday argued that the popularity of theMacintosh Quadra 700 was the turning point for computer manufacturers to move over to the tower form factor en masse. The tower form factor of the Quadra 700 was by necessity: common peripherals of the Quadra were the relatively extremely heavy color CRTmonitors offered by Apple (those whose screens measured 20 inches and over diagonally could weigh 80 lbs or more) favored by thedesktop publishing industry during the 1990s. Such monitors threatened to crush the plastic frames of theMacintosh IIcx andMacintosh IIci; customers might have been tempted to fit such heavy monitors atop the IIcx and IIci because of their horizontal form factor.[25]
| Micro |
| ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Midrange | |||||||||||||||||||||||
| Large | |||||||||||||||||||||||
| Others | |||||||||||||||||||||||
