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The EISA bus is obsolete and should not be used for new systems.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-AT Board Size

PC [ISA] EISA Connector Pin-Out
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 Token Ring NIC 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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Modified 3/05/12
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