ESA
VESA stands for Video Electronics Standards Association, but the easy way to remember the VESA bus is to think “Visa,” the popular credit card company, and associate that with high costs. The VESA bus was the first 32-bit video bus and also the first video-only bus in general. One of its limitations was the initial costs of the expansion graphics cards associated with the bus. It is no longer found on motherboards built today and it is rather difficult to find VESA cards. VESA is seen as the precursor to the very popular AGP bus, which is nothing more than an improvement on the VESA design.
MCA
Basically, this was a failed attempt by IBM at dominating the bus market with a proprietary architecture. MCA, or Micro Channel Architecture, extended ISA by being 32 or 16 bit, a large improvement. In addition, it was able to utilize bus mastering, which is the ability of an expansion bus to control itself – i.e. be a standalone unit, with its own processor and everything. These were rapid improvements to the existing ISA architecture. However, many manufacturers were quite tart over the proprietary nature of the architecture and went on to create…
EISA
After the creation of the MCA bus, a large group of computer manufacturers, zealously led by Compaq, agreed to create a new standard. It too utilized a 32-bit architecture, bus mastering, and even a whole new idea to the scene, “Automated setup,” which is seen by most as a precursor to the modern plug-and-play technology. It was never embraced by desktop PC makers, despite the effort, but it secured a niche in the server market.
PCI
PCI was developed as the Peripheral Component Interconnect to be a 32-bit or 64-bit bus that is faster (33 MHz.), universally accepted (Intel-backed), and very adaptable. The PCI bus supports bus mastering, burst mode, and is also completely Plug-and-Play compatible. The PCI bus utilizes direct CPU communication through the host bridge for optimal performance.
PCI-X
A more recent development is the PCI-X bus, which extends PCI to faster speeds and makes it 64-bit more often than not. It has all of the PCI features and is backwards compatible with PCI cards.
AGP
The infamous AGP bus can be said of something of a combination of the concept of the VL (VESA Local) bus and the performance and reliability of an offshoot of the PCI technology. The AGP bus runs at 32-256 bits (in theory) and is very fast in general. In addition, AGP throughput is much higher than VESA or even PCI. AGP is a niche bus for graphics cards.
The PCMech.com weekly newsletter has been running strong for over 8 years. Sign up to get tech news, updates and exclusive content - right in your inbox. Also get (several) free gifts.
