Backplane

The term backplane, backplane or back plate is used in electronics in various forms. It is both a technical structure in electronic devices to add more electronic assemblies. On the other hand, is a specific part of the infrastructure of computer networks is so called.

Use in electronic equipment

Backplane is called the back wall of an electronic device having a plurality of slots for insertion assemblies ( cards ). The backplane carries the Connectors for plug assemblies and connecting them electrically. In general, it is a passive device, there are so equipped no active components such as ICs and passive components such as resistors or capacitors on it.

In the early days of electronics consisted backplanes racks were mounted in the connector for plug-in cards side by side. The electrical connections of the individual pins between the connectors was done by hand and in the air, usually organized into bundled strands of wire ( see figure attached), and for other equipment but also completely free (Example: Early Cray models).

Backplane wiring of a Cray -2

Nowadays, the backplane is often performed as a multi-layer printed circuit board and is provided with holes during manufacture, in which the connectors are pressed. Since it will not be loaded, it will not run through the solder bath. In the manufacture of devices it is therefore a finished part that is supplied by companies that have specialized in PCB manufacturing, not the assembly of printed circuit boards.

The electrical connections that the backplane between the slots may be made ​​very different, and to determine the architecture of the device. Perform the connections between several identical slots to a central assembly, one speaks of a star-shaped wiring. The individual modules can then communicate with each other is not, but only the central module. If similar units are linked together, so this represents a bus dar. This type of connection via a backplane requires a bus arbitration, a provision which prevents simultaneous write to the bus by different components. This process is rate-limiting for the data traffic on the bus and usually a device identifier. For example, the performance of a router described with a throughput of 1 Gbit / s, this usually means that the bus on the backplane can make these data throughput.

One older bus for backplanes is the VMEbus.

Often backplanes are also used in the computer field in servers and mainframes. One (or more ) plug-in card (s) with processors is plugged into the backplane. You can then use the PCI, ISA or other interfaces, for example.

Use in switches

A backplane is also a high-speed bus for switches. A switch controls the communication in computer networks. The individual ports of a switch are connected to the backplane, wherein said compound is different from the matrix switch. Unlike the matrix architecture, all ports are not connected to each other but are located on a data bus.

A backplane can have a specific data transfer rate that is ( s Gbps or Gbit / ) can indicate, for example, in gigabits per second. Important is the value of the data transmission rate with an anticipated heavy traffic on a network. Namely, if all ports of a switch in full duplex mode are utilized, such as 8 ports with 100 Mbit / s by 2, then the data rate of the backplane should be at least 1.6 Gbps. Otherwise, there is a blocking ( blocking English ) individual data packets. A switch architecture, which is reported as non-blocking, ie has an available data rate that is higher than the maximum possible traffic. Each port can be set so that at any time the full for him data transfer rate available.

• Construction and connection technology of the electronics