The IBM Micro Channel Architecture [MCA] bus was released around 1987
operating on the Intel 286 processor, then later on the 386
series of processors within the IBM PS2 series of computers. The MCA bus
was an IBM proprietary interface. The MCA (Micro Channel Architecture)
bus was used as a PC expansion bus, allowing expansion cards to be
plugged into MCA slots on the Mother Board. The MCA bus is Obsolete;
running at a 10MHz bus speed using either a 16 or 32 bit wide data bus,
uP independent, asynchronous. With bus enhancements the speed reaches
80MBps, using clock doubling. The MCI bus only appeared on IBM PS2 series
of computers which have been off the
market for many years now. The pinout for the MCA bus is shown in the
table below; with the 'A' and 'C' connectors located on the component
side of the board and the 'B' and 'D' connectors located on the circuit
side of the board [back-side].
The MCA bus was not backwards compatible with the original ISA bus, and was only
produced by IBM; however the proprietary MCA bus was licensed to a few
other companies. The MCA bus was in competition with the EISA bus, but
was rendered obsolete by the introduction of the PCI bus. The MCA interface is
obsolete and should not be used for new designs. However, legacy systems
may still include MCA boards.
Graphic of PC AT Card showing the location of the J1 and J2 pins.
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| 1 | VSYNC | ESYNC | +5V | D8 |
| 2 | HSYNC | GND | D10 | D9 |
| 3 | BLANC | P5 | D11 | GND |
| 4 | GND | P4 | D13 | D12 |
| 5 | P6 | P3 | +12V | D14 |
| 6 | EDCLK | GND | Reserved | D15 |
| 7 | DCLK | P2 | SBHE | GND |
| 8 | GND | P1 | CD DS 16 | IORQ10 |
| 9 | P7 | P0 | +5V | IORQ11 |
| 10 | EVIDEO | GND | IRQ14 | IORQ12 |
| 11 | CD/SETUP | Audio/GND | IRQ15 | GND |
| 12 | MADE24 | Audio | - | - |
| 13 | GND | GND | - | - |
| 14 | A11 | OsciLlator | - | - |
| 15 | A10 | GND | - | - |
| 16 | A9 | A23 | - | - |
| 17 | +5V | A22 | - | - |
| 18 | A8 | A21 | - | - |
| 19 | A7 | GND | - | - |
| 20 | A6 | A20 | - | - |
| 21 | +5V | A19 | - | - |
| 22 | A5 | A18 | - | - |
| 23 | A4 | GND | - | - |
| 24 | A3 | A17 | - | - |
| 25 | +5V | A16 | - | - |
| 26 | A2 | A15 | - | - |
| 27 | A1 | GND | - | - |
| 28 | A0 | A14 | - | - |
| 29 | +12V | A13 | - | - |
| 30 | ADL | A12 | - | - |
| 31 | PREEMPT | GND | - | - |
| 32 | BURST | IRQ9 | - | - |
| 33 | -12V | IRQ3 | - | - |
| 34 | ARB0 | IRQ4 | - | - |
| 35 | ARB1 | GND | - | - |
| 36 | ARB2 | IRQ5 | - | - |
| 37 | -12V | IRQ6 | - | - |
| 38 | ARB3 | IRQ7 | - | - |
| 39 | ARB/GNT | GND | - | - |
| 40 | TC | Reserved | - | - |
| 41 | +5V | Reserved | - | - |
| 42 | S0 | CHCK | - | - |
| 43 | S1 | GND | - | - |
| 44 | M/IO | CMD | - | - |
| 45 | +12V | CHROYRTN | - | - |
| 46 | CD CHRDY | CD SFDBK | - | - |
| 47 | D0 | GND | - | - |
| 48 | D2 | D1 | - | - |
| 49 | +5V | D3 | - | - |
| 50 | D5 | D4 | - | - |
| 51 | D6 | GND | - | - |
| 52 | D7 | CHRESET | - | - |
| 53 | GND | Reserved | - | - |
| 54 | DS 16 RIN | Reserved | - | - |
| 55 | REFRESH | GND | - | - |
| The MCA bus uses the J1 A/B rows, and J2 [C/D rows] connectors. The fingers are copper strips on the PWB spaced on 0.1 inch centers. The IBM MCA bus was an up-grade to the original PCAT ISA bus and was not back-wards compatible. The connector positions and relationship to the board are detailed above. The MCA bus is obsolete and should not be used with new computer systems. Card Edge connector manufacturers are listed on the connector manufacturers page. |
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Back to the main Personal Computer Expansion Bus page. Engineering Design Key words: IBM, PC, Personal Computer, Micro Channel Architecture, PCAT, PCXT, ISA, Industry Standard Architecture Bus, Pinout, P2/J2 Pinouts, P1/J1 Pin-out, J1 (A/B), J2 (C/D), Pin Outs, Connector, Signal Names, Pin descriptions, Card size, PWB Board Dimensions, Mechanics Description, Electrical Interface, IC, Parallel Bus, Physical Interface, Obsolete, Legacy, Out-Dated. |
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