CertiGuide to A+ (A+ 4 Real)  9  Chapter 8: Motherboards

Expansion Buses 1 MCA

ISA stands for Industry Standard Architecture and it was the first expansion bus widely used on PC motherboards. The ISA expansion bus was originally developed by IBM for the AT motherboard form factor. It was 8 bits wide and rated at 8.33 MHz. ISA was later expanded to provide a 16-bit wide bus that was backwardly compatible with 8-bit ISA devices. One of the major downsides to the ISA bus was that only one ISA device at a time could use the bus. If for example, an ISA modem were dialing up an Internet connection, an ISA sound card would not be able to function simultaneously because the bus was “busy”. The EISA (Extended Industry Standard Architecture) bus was developed in 1988, with a rated speed of 33 MHz, but never became very popular. The EISA bus was backwardly compatible with 8 bit as well as 16-bit technology. ISA was phased out of motherboard manufacturing in 1999 because it was outclassed by PCI bus technology that could handle 32 bit data transfers. The ISA bus became obsolete because it became too slow.

Expansion Buses 1 MCA