U is the unit representing the external dimensions of modular racks, and the detailed dimensions are determined by the American Electronics Industry Association (eia) as an industry group. The basic unit of thickness is 4.445cm. 1u is 4.445cm, 2u is 8.89cm, which is twice as much as 1u (and so on).

Chassis generally includes shell, bracket, various switches and indicator lights on the panel, etc. The shell is made of steel plate and plastic with high hardness, which mainly protects the internal components of the chassis. The bracket is mainly used to fix the motherboard, power supply and various drivers.

From the size point of view, all the series of BTX platform motherboards are not smaller than ATX motherboards, so the development of BTX is not a smaller desktop computer. More flexible circuit wiring and modular component area are the focus of BTX. The most obvious difference between BTX chassis and ATX chassis is that the side panel that can only be opened on the left side has been changed to the right side.

The concept of u

The reason for specifying the server size is to keep the server in an appropriate size to be placed on an iron or aluminum rack. There are screw holes for fixing the servers on the rack, so that they can be numbered with the screw holes of the servers, and then fixed with screws to facilitate the space required for installing each server.

The specified size is a multiple of the server width of 48.26 cm (19 inch) and the height of 1.75 inch (4.445 cm). Because the width is 19 inch, the rack that meets this requirement is sometimes called "19 inch rack". The basic unit of thickness is 4.445cm. 1U is 4.445cm, and 2U is 8.89cm, which is twice as much as 1U.

The so-called "1U PC server" is a product with a shape conforming to EIA specifications and a thickness of 4.445cm. Products designed to fit into a 19-inch cabinet are generally called rack servers.

Refer to Baidu Encyclopedia-1u for the above contents.