Buses

Buses

• A bus is a data pathway between several hardware components inside or outside a computer. 
• It not only connects the parts of the CPU to each other, but also links the CPU with other important hardware. 

• The other important hardware includes memory, a disk control unit, a terminal control unit, a printer control unit, and a communications control unit. 
• The capacity of a bus is expressed as bits. 
• A larger capacity bus is faster in data transfer.

Three Main Bus Architectures

o    ISA (Industry Standard Architecture): ISA is pronounced i- suh. This is the original PC bus architecture. It includes the 8-bit and 16-bit  buses in IBM personal computer series and compatibles. Now, it refers specially to the 16-bit AT bus.

o    MCA (Micro Channel Architecture): A 32-bit bus used in IBM P/S 2 series and other IBM models. This architecture allows multiprocessing that allows several processors to work simultaneously. Micro channel architecture is not compatible with PC bus architecture.

o    EISA (Extended Industry Standard Architecture): EISA is pronounced eesa. This is a bus standard for PCs that extends the AT bus  architecture to a 32-bit bus. This architecture also allows more than one CPU to share the bus. The purpose of EISA is to extend and amend the old ISA standard, so that all existing AT expansion boards can work with an EISA slot.