BACKPLANE

A 'backplane' (or "backplane system") is a circuit board (usually a printed circuit board) that connects several connectors in parallel to each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a backbone to connect several printed circuit board cards together to make up a complete computer system. One popular early computer system that used this approach was called the S-100 bus because the connectors used had one hundred pins. Early personal computers like the Apple II and the IBM PC integrated an internal backplane for expansion cards.
A backplane is generally differentiated from a motherboard by the lack of on-board processing power where the CPU is on a plug-in card.
Backplanes are normally used in preference to cables because of their greater reliability. In a cabled system, the cables need to be flexed every time that a card is added to or removed from the system; and this flexing eventually causes mechanical failures. A backplane does not suffer from this problem, so its service life is limited only by the longevity of its connectors. For example, the DIN 41612 connectors used in the VMEbus system can withstand 50 to 500 insertions and removals (called ''mating cycles''), depending on their quality.

Contents

Active backplanes

Backplanes in storage

Companies that make backplanes

Articles on SGPIO Backplane Controllers

SES Backplane Controllers

Midplane

See also

Active backplanes

Backplanes have grown in complexity from the simple ISA (used in the original IBM PC) or S-100 style where all the connectors were connected to a common bus.
Because of limitations inherent in the PCI specification for driving slots, backplanes are now offered as 'passive' and 'active'.
Passive backplanes offer no active bus driving circuitry. Any desired arbitration logic is placed on the daughter cards. Active backplanes include chips which buffer the various signals to the slots.
The distinction between the two isn't always very clear, but may become an important issue if a whole system is expected to have no single point of failure. A passive backplane, even if it ''is'' single is not usually considered a SPOF. Active backplanes are more complicated and thus have a non-zero risk of malfunction.

Backplanes in storage

Backplanes have also become common place for connecting multiple hard drives to a single disk array controller. Backplanes are commonly found in disk enclosures, disk arrays, and servers.
Click here for pictures of backplanes with explanation of connectors etc
Backplanes for SAS and SATA HDDs most commonly use the SGPIO protocol as means of communication between the HBA and the backplane.

Companies that make backplanes

American Megatrends, Inc. supplies the storage industry with SGPIO and SES Backplane Controllers.
Their main customers are OEM and ODM companies in US, Taiwan, Japan and China. AMI has been designing backplanes for major OEMs since 1998 and providing shipping backplane management controllers for SCSI since 1999. In 2002 AMI came out with a backplane controller for IDE, based on a patent filed by the company. Their first backplane controller that supported SATA was released in 2003. Although AMI is mostly known as a major provider of BIOS they have been providing backplanes and backplane controller to most major OEMs. AMIs backplane products are found on backplanes from SuperMicro, Sun Microsystems, IBM, Quanta, Flextronix, Rackable Systems, and many smaller Taiwan based computer companies.
American Megatrends on Wikipedia
American Megatrends, Inc. Company Website AMI
Backplane Controllers from AMI

Articles on SGPIO Backplane Controllers

Backplane Controller ASIC by AMI MG9073S.

SES Backplane Controllers

Midplane

Whereas cards and devices connect to only one side of a backplane, a midplane has cards and devices connected to both sides. This ability to plug cards into either side of a midplane is often useful in larger systems made up primarily of modules attached to the midplane. Midplane system design is popular in networking and telecommunications equipment where one side of the chassis accepts system processing cards and the other side of the chassis accepts network interface cards. Most blade server systems also use this type of design, with server blades on one side, and peripheral (power, networking, and other I/O) and service modules on the other.

See also

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