MCA Board Pinout and Signal Names


MCA Expansion Bus Description

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 The MCA bus is Obsolete; running at a 10MHz bus speed using either a 16 or 32 bit wide data bus, [asynchronous and uP independent]. 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The MCA interface is obsolete and should not be used for new designs.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.





MCA Bus Pinout and Signal Names

Graphic of PC AT Card showing the location of the J1 and J2 pins.

IBM PC MCA Connector Pin Out
Pin
J1
J2
#
A Row
B Row
C Row
D Row
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 Pins
Not Used
Pins
Not Used
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.

Personal Computer Expansion Bus page.
A related topic; Intel Processor Release Dates

The MCA Pinout table indicates the pins that are not used on J2; however there could be copper fingers on the board.
Of course no traces would be routed to the fingers, some times it's just cheaper to continue the finger pattern.
The MCA interface is obsolete so the pin descriptions are fixed as listed and will never change;
The pins labeled Reserved will never be used in a future interface change because the MCA interface is Out-dated.
Interfaces that are out dated but may still require a new design interface are called legacy interfaces.


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Modified 2/4/12
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