PC EISA Card Pinout and Board Size

The EISA (Extended Industry Standard Architecture) or Enhanced ISA bus operated at 8MHz using a 8/16/32 bit data bus. The EISA interface was another PC Expansion Bus which was also compatible with ISA. An ISA card will work in a EISA slot, but an EISA board will not work in an AT slot. All of the PC-XT and PC-AT fingers reside on an EISA board/connector. The actual EISA fingers (pin) reside below the XT and AT fingers on an EISA board. The EISA bus (in one mode) used both edges of the clock, with the rising edge used to output address, and the falling edge to place the data on the bus. Three other transfer modes were available. The EISA bus does not allow the board skirts that were common with the older XT cards. The EISA cards are the same size as the AT cards [shown below].
The new address lines are called "LA#", and all address lines are latched. Refer to the EISA Pinout table below for EISA signal names and pin out information.

The Board size and Pinout for the Extended Industry Standard Architecture [EISA] bus is shown below. The EISA bus may also be called the Enhanced ISA bus.
The EISA bus is obsolete and should not be used for new systems. However the pin out table may be used for legacy computer systems.

PC Card Size
PC-AT /PCI Board Size

**PC [ISA] EISA Connector Pin-Out**
Pin	J1				J2
#	A Row	B Row	E Row	F Row	C Row	D Row	G Row	H Row
1	Channel Check	Ground	CMD	GND	System Enable	Memory 16 bit select	LA7	LA8
2	Data 7	Reset	START	+5 volt	Unlatched Address 22	I/O 16bit Chip Select	GND	LA6
3	Data 6	+5v	EXRDY	+5 volt	Unlatched Address 23	IRQ10	LA4	LA5
4	Data 5	IRQ9	EX32	Reserved	Unlatched Address 21	IRQ11	LA3	+5 volt
5	Data 4	-5v	GND	Reserved	Unlatched Address 20	IRQ12	GND	LA2
6	Data 3	DMA Request 2	KEY	KEY	Unlatched Address 19	IRQ15	KEY	KEY
7	Data 2	-12v	EX16	Reserved	Unlatched Address 18	IRQ14	SD17	SD16
8	Data 1	Zero Wait State	SLBURST	Reserved	Unlatched Address 17	DMA ACK0	SD19	SD18
9	Data 0	+12v	MSBURST	+12 volt	Memory Read	DMA Request 0	SD20	GND
10	I/O Channel Ready	Ground	W/R	M/IO	Memory Write	DMA ACK5	SD22	SD21
11	Address Enable	Real Memory Write	GND	LOCK	Data 8	DMA Request 5	GND	SD23
12	Address 19	Real Memory Read	RESERVED	RESERVED	Data 9	DMA ACK6	SD25	SD24
13	Address 18	I/O Write	RESERVED	GND	Data 10	DMA Request 6	SD26	GND
14	Address 17	I/O Read	RESERVED	RESERVED	Data 11	DMA ACK7	SD28	SD27
15	Address 16	DMA ACK3	GND	BE3	Data 12	DMA request 7	KEY	KEY
16	Address 15	DMA Request 3	KEY	KEY	Data 13	+5v	GND	SD29
17	Address 14	DMA ACK1	BE1	BE2	Data 14	Master	SD30	+5 volts
18	Address 13	DMA Request 1	LA31	BEQ	Data 15	Ground	SD31	+5 volts
19	Address 12	Refresh	GND	GND	N/A	N/A	MREQ	MAK
20	Address 11	CLK	LA30	+5 volts			N/A	N/A
21	Address 10	IRQ7	LA28	BEQ
22	Address 9	IRQ6	LA27	GND
23	Address 8	IRQ5	LA25	LA26
24	Address 7	IRQ4	GND	LA24
25	Address 6	IRQ3	KEY	KEY
26	Address 5	DMA ACK2	LA15	LA16
27	Address 4	Terminal Count	LA13	LA14
28	Address 3	Address Latch En	LA12	+5 volt
29	Address 2	+5v	LA11	+5 volt
30	Address 1	Oscillator	GND	GND
31	Address 0	Ground	LA9	LA10

EISA PC Card

The PCXT bus pinout uses the J1 A/B rows, and a PCAT bus pinout uses the J1 [A/B rows] and J2 [C/D rows] connectors. The PC EISA pinout uses all rows of both J1 and J2. The EISA bus added rows 'E', 'F', 'G', and 'H' under the XT and AT pins. The fingers are copper strips on the PWB spaced on 0.1 inch centers.

The PCAT bus [ISA] was an up-grade to the original PCXT bus, and the EISA bus was an up-grade to the PC-AT bus. An ISA card will work in a EISA slot, but an EISA card will not work in an AT slot. The Pin Out for both bus types are shown in the table above. The connector positions and relationship to the board are shown in the two figures at the top of the page. Both figures show a PCAT card, but the first figure also shows an attached PCI bus.

Example dimensions for the card sizes are provided. Some of the signal names provided in the pin-out table are not correct terms. For example the Address lines called out above would be called SA#, and the Data lines would be called SD#. The IBM compatible AT card used the standard (edge) connector provided by the XT bus and added an additional edge connector behind that with the same pin-spacing @ 0.1 inch center-to-center. The additional connector has only 38 fingers (19 per side), while the XT connector had 62 fingers (32 per side). The Personal Computer Motherboard could then accept either an 8 or 16 bit card in an 8 bit slot (XT), or (if the connector was provided) a 16 bit card in an AT slot.

A maximum number of 8 Expansion slots were provided on IBM compatible mother boards.

Of course this page was originally written when it was possible to find a EISA card in service.
These days the obsolete EISA interface is no longer used and is out-of-date.
Any EISA card would have been replaced by some other board long ago, even with the long cycles of military designs or products.
As with a number of legacy interfaces, the information is offered as is, but no attempt should be made to use the data.
This data is obsolete and should not be used in any new design. Well the approach and speeds are obsolete.
Notice that most of the integrated circuits used in the photo of the EISA card are low density LSI glue logic ICs.
Current designs might use a few surface mount SOICs, but much of the circuitry could be contained within a single FPGA.

Return to the main PC AT bus page [ISA Expansion Bus].

Topic Navigation: Engineering Home > Interface Buses > Personal Computer Buses > PC AT Expansion Bus > EISA Expansion Card.


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