Pizza box form factor

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The Macintosh LC's typical "pizza box" case

In computing, a pizza box is a style of case for computers. They tend to be very thin, normally one or two rack units (1U or 2U) in height, making them wide and flat. The result is a case that looks like boxes used to deliver pizza.

The first computers generally referred to as pizza box machines were Sun Microsystems desktop workstations sold in the late 1980s, most notably the SPARCstation 1. Other famous examples include the SGI Indy, the NeXTstation, Macintosh LC, and Amiga 1000.

The original SPARCstation 1 design included an expansion bus technology, SBus, expressly designed for the form factor; expansion cards were small, especially in comparison to other expansion cards in use at the time such as VMEbus, and were mounted horizontally instead of vertically. PC compatible computers in this type of case typically use the PCI expansion bus and require special low profile expansion cards, shorter than the PCI cards used in regular PCs.^[1]

The density of compute power and stackability of pizza box systems also made them attractive for use in data centers. Systems originally designed for desktop use were placed on shelves inside of 19-inch racks, sometimes requiring that part of the case be cut off in order for them to fit. Servers in this form factor are now designed for rack mounting.

The pizza box style has mostly fallen from use for desktop computing, as concerns such as cooling and expansion capabilities have made tower and minitower designs the de facto standard. Taller versions of the pizza box design exist, but these are usually known as "desktop cases"; they have roughly the same dimensions as a mini tower, but are designed to lay flat on a desk.