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 The MCA bus is Obsolete; running at a 10MHz bus speed using either a 16 or 32 bit wide data bus, [asynchronous and uP independent].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The MCA interface is obsolete and should not be used for new designs.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