bus is a commonly used industrial computing
standard which provides a flexible and robust framework for building several kinds of systems.
The basic VME system consists of a backplane and a card cage; the card cage is a more durable and stable system than almost any PC case configuration, designed with the notion of shipboard use under missile attack in mind. The backplane is also phenomenally versatile; while originally designed for up to 32 bit data transfers and addressing, it has been updated to accommodate multiplexed 64 bit data and addresses, and even includes 64 user-definable pins which can be used for just about anything, including analog signals. The bus also provides control lines and protocols for interrupt handling and allows up to 20 CPU boards to share a single bus, making it an ideal multiprocessor system (commercially available boards include AMD Athlon and IBM 970 CPUs, and these can peacefully coexist.)
The basic advantage of the VME bus is versatility; there is very little that cannot be done on the system, ranging from industrial control, mission critical system monitoring, military applications, and commercial audio and video systems, for example. However for many applications a clear disadvantage comes in cost and complexity; with 184 pins per card slot in a standard backplane (most of which have 20 or so slots) there are a lot of signal lines involved, and specialized master and slave boards can range in cost from several hundred to tens of thousands of dollars. Additionally the 6U profile, while conveniently rack mountable, may not be ideal for most (if any) consumer applications.