Micro Channel Architecture (MCA)
In 1986, the market came to be dominated by the new 386 machines with their 32-bit architecture. Most PC manufacturers stuck to the same basic ISA design and MS-DOS. Expansion devices based on ISA technology for the 286 AT class machines could be placed in a new 386 clone without problems.
IBM, however, was feeling the pinch of competition from cheaper clones, and sought to retain its dominance in the PC market. IBM designers produced a new version of the PC, the PS/2 (Personal System/2) and created a proprietary expansion bus called Micro Channel Architecture (MCA) as part of the design. Running at 10 MHz, it offered more performance and provided a 32-bit data path. It was also totally incompatible with older ISA cards.
A feature of MCA is its ability to "self-configure" devices. Unlike devices that use technology in which the PC configures itself automatically to work with peripherals such as monitors, modems, and printers, an MCA device always comes with a configuration disk. When installing a new device in an MCA computer, insert the configuration disk (when prompted), and the IRQs, I/O addresses, and DMA channels will be configured automatically. (IRQs, I/O addresses, and DMA channels are discussed in detail in the next lesson.) An MCA bus is shown in Figure 10.2.
The PS/2 never gained enough market share to compete with the 386. MCA cards were few and far between, and more expensive than competing interface designs.
Figure 10.2 MCA bus
MCA is now a lost technology. As a computer technician, you will not encounter MCA on new computers. However, it is still found in some older machines, and you will need to know how to identify it. If a customer brings in a PS/2 machine for service, be sure to obtain the configuration disks for the computer as well as any MCA cards that go with it.