Micro Chanel Structures

MCA ( Micro Chanel Structures ) was a drunk proposed by IBM in 1987 in improvement of the bus ISA, alias PC/AT. Charts ISA were however not compatible with bus MCA.

Bus MCA appeared with the series of computers IBM Personal System/2. The first IBM RS/6000 (7006…), work stations based on PowerPC used also this bus.

Of color chestnut, it transmitted information per packages of 32 bits to a speed of 33 MHz.

This bus exceeded its contemporaries ISA and EISA and had characteristics close to the NCV, which will come only a few years later.

The MCA had a strongly anti-disturbed system of mass in order to avoid the parasitic electromagnetic interferences.

The configuration of charts MCA was unusual for the time, in the sense that it was entirely carried out by diskette, with starting, via the BIOS. No rider of configuration (for IRQ…) did not exist on charts MCA. Plug' N Play had obviously directed its design partly.

This new architecture owner - but also proposed under license - was to replace existing bus ISA, with the capacities too limited for new the Intel 80386. IBM undoubtedly hoped also to recover the control of the market partly, because although the standard IBM PC became an immense success, the share of IBM in this market decreased as spread clones of them.

Bus MCA due to face the opposition of Compaq which denounced the " closing of the standard" by IBM. Compaq re-elects the " then; bus AT" 16 bits, expression deposited by IBM, in the bus ISA, and the fact of evolving/moving in the bus EISA.

Bus MCA, handicapped by its incompatibility with old charts ISA, by its price and its technical complexity, and by the license that IBM claimed, did not have success that IBM hoped. The manufacturers could buy at IBM a license of bus MCA allowing them to manufacture and sell clones of IBM PS/2. These " clones autorisés" were however rare. For the anecdote, Tandy acquired such a license.

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