ISA Backplane



ISA Backplane board was designed by Sergey Kiselev ( and is designed to be used together with the Xi 8088 processor board, but it can be used with other ISA SBC boards. In addition to eight parallelly connected ISA slots this backplane includes an ATX power on/off circuit, a Port 80h POST display, a -5V regulator (most ATX power supplies don't supply -5V, but it can be required for some older ISA cards), serial port header, and a prototyping space.


  • 8 ISA Slots
  • Micro ATX compatible form factor
  • ATX power control circuit
  • -5V regulator
  • Port 80h POST diagnostic display
  • 5 Power indicator LEDs (standby, 5V, -5V, 12V, -12V)
  • Serial DE9M header
  • Reset button and header

Hardware Documentation

Current Board Revision: Rev 1.1

Board: isa_blackplane-1.1-brd.pdf

Schematic: isa_backplane-1.1-sch.pdf

Manufacturing Files:

KiCAD Files:

Note: The only change between Rev 1.0 and Rev 1.1 was a slight re-positioning of the main ATX power connector. The Rev 1.0 files are archived here.

Build Information

Jumpers, Connectors, and Switches

FIXME Create a nice graphic of the jumpers/switches on this board! FIXME

It is recommended to solder wire bridges instead of J2 - J4 according to your 7-segment LED display and binary to 7-segment decoder type. Please refer to Bill of Materials section for displays' and decoders' selection.

Bill of Materials (BOM)

Component TypeReferenceDescriptionQuantityPossible sources and notes
PCB ISA Backplane PCB Version 1.1 1 Order from Todd Goodman, see RetroBrew Computers Board Inventory
Capacitor C1 - C51 10 uF ceramic, 5.08 mm lead spacing 51 Mouser 810-FK24X5R1C106K
Note: Can be replaced with tantalum or electrolytic capacitors
Capacitor C52 1 uF ceramic, 5.08 mm lead spacing 1 Mouser 810-FK24X7R1C105K
Note: Can be replaced with tantalum or electrolytic capacitors
Capacitor C53 - C59 0.1 uF ceramic, 5.08 mm lead spacing 7 Mouser 810-FK28X7R1H104K, 80-C323C104K5R
Jameco 25523
Connector BUS1 - BUS8 ISA Edge connector, 98 pin 8 Mouser 587-395-098-520-350
Connector J1 - J4 3×1 pin header 4 Mouser 649-69190-103HLF, 649-78229-103HLF
Jameco 109576
Connector P1, P2, P6, P7 2×1 pin header 4 Mouser 649-78229-102HLF
Jameco 108338
Connector P3 ATX power connector 1 Mouser 538-46015-2006
Jameco (was 365149)
Connector P4 5×2 pin header 1 Mouser 649-68602-110HLF
Connector P5 DE9M, right angle PCB mount 1 Mouser 806-K22X-E9P-N-99 (teal color), 806-K22X-E9P-N, 571-7478404
Jameco 104943, 614441, 614459, 614432
Diode D6, D7 1N4148 2 Mouser 512-1N4148, 771-1N4148,143
Jameco 36038, 179215
LED D1 - D5 5 mm LED 5 Mouser: Search for T-1 3/4 LED lamps
Jameco 790225 (red, diffused), 107393 (orange, diffused), 697549 (yellow, diffused), 697531(green, diffused), 138691 (blue, diffused)
Note: Use different colors for a nicer look
LED Display S1 2 digit 7-segment LED display,0.56“ character height, 18 pin, 15.24 mm (0.6” between pin rows) 1 Mouser 604-DC56-11YWA (common cathode Red)
Jameco 24707 (common cathode, orange), search for more options
Note: Pick either common cathode type or common anode type according to the decoder IC you're planning to use.
Resistor R1, R2 10 kOhm, 1/4 W 2 Mouser 291-10K-RC
Jameco 691104
Resistor R3, R4 1.5 kOhm, 1/4 W 2 Mouser 291-1.5K-RC
Resistor R5, R6 1 kOhm, 1/4 W 2 Mouser 291-1K-RC
Resistor R7 - R11 470 Ohm, 1/4 W 5 Mouser 291-470-RC
Jameco 690785
Resistor Array RR1, RR2 470 Ohm, 16 pin DIP, isolated resistor array 2 Mouser: 652-4116R-1LF-470
Note: Can be replaced with 16 x 470 Ohm resistors
Trimmer Resistor RV1 50 kOhm 1 Mouser: 652-3362P-1-503LF
Note: This trimmer is only needed if using D346D or D347D decoders (U1, U2)
Switch SW1,SW2 6mm Tactile Switch 2 Mouser: 653-B3F-1000
IC U1, U2 7 segment decoder 2 Note: Please refer to the table below for proper decoder/display configuration

74HCT4511/74HC4511 (common cathode):
Mouser: 771-HCT4511N652, 595-CD74HCT4511EE4, 595-CD74HCT4511E, 771-74HC4511N, 595-CD74HC4511EE4

CD4511 (common cathode):
Mouser: 595-CD4511BE, 595-CD4511BEE4
Jameco: 13493, 895377

74LS47 (common anode):
Mouser: 595-SN74LS47NE4, 595-SN74LS47N
Jameco: 47790, 295582; Unicorn electronics

74LS247 (common anode, similar to 74LS47, but 6 and 9 with tails):
Mouser: 595-SN74LS247NE4, 595-SN74LS247N
Jameco: 47247

74LS48 (common cathode):
Jameco: 47811

DM9368 (common cathode):
Intertex Electronics, or eBay

D346D (common anode): Ask your European friend
IC U3 74LS688 1 Mouser: 595-CD74HCT688E, 771-74HCT688N, 595-SN74LS688N
IC U4 74LS574 1 Mouser: 595-SN74HCT574N, 595-SN74ALS574BN, 595-SN74F574N
IC U5 74HCT74 1 Mouser: 771-74HCT74N, 595-SN74HCT74N, 595-SN74HCT74NE4, 595-CD74HCT74E
IC U6 74LS32 1 Mouser: 595-SN74ALS32N
IC U7 74HCT14 1 Mouser: 595-SN74AHCT14N, 595-SN74HCT14NE4, 595-SN74HCT14N, 595-CD74HCT14E
IC U8 7905 1 Mouser: 512-LM7905CT
Note: This IC is optional, and only required if you need -5V voltage, but your ATX power supply doesn't provide it.
IC Socket U5, U6, U7 14 pin 300 mil DIP socket 3 Mouser 517-4814-3000-CP, 649-DILB14P-223TLF
Jameco 37162
IC Socket U1, U2 16 pin 300 mil DIP socket 2 Mouser 517-4816-3000-CP, 649-DILB16P-223TLF
Jameco 37373
IC Socket U3, U4 20 pin 300 mil DIP socket 2 Mouser 649-DILB20P-223TLF, 517-4820-3000-CP
Jameco 112248

7-Segment Decoders and Matching Displays

The ISA Backplane board supports a variety of 7-segment decoders and common anode / common cathode type LED displays. Please use the following table to determine the proper configuration.

7-Segment Decoder Type Hexadecimal Support Matching Display Type J2 J3 J4 Built in current limiters1
74LS47, 74LS247 Limited - Displays distinct figures for codes A-F Common anode 2-3 2-3 2-3 No
74LS48, 74LS248 Limited - Displays distinct figures for codes A-F Common cathode 1-2 2-3 2-3 No
CD4511, MC14511, 74HCT4511 No - Displays nothing (blank) for codes A-F Common cathode 1-2 2-3 1-2 No
Mitel MD4311BE Yes Common cathode 1-2 2-3 1-2 No
DM9368 Yes Common cathode 1-2 1-2 2-3 Yes
DM9370 Yes Common anode 2-3 1-2 2-3 No
DM9374 Limited - Displays distinct figures for codes A-F Common anode 2-3 1-2 2-3 Yes
D345D Yes Common anode 2-3 1-2 2-3 No
D346D Yes Common anode 2-3 Trim2 2-3 Yes
D347D Limited - Displays distinct figures for codes A-F Common anode 2-3 1-2 2-3 No
D348D Limited - Displays distinct figures for codes A-F Common anode 2-3 Trim2 2-3 Yes
  1. No need for current limiting resistor arrays (RR1, RR2), two 470 Ohm resistors should be used to limit current for the decimal point segment.These resistors should be installed between pins 8 and 9 of RR1 and RR2.
  2. For decoders D346D and D348D the RV1 trimmer should be installed instead of the J3. This trimmer is used to adjust the intensity of the LED display.

Replacement Notes

  • It is recommended to use CMOS parts (74HCT, 74AHCT) for U5 and U7
  • Other logic can be from any TTL compatible series (74AHCT, 74HCT, 74LS, 74ALS, 74F).

File List

FilenameFilesizeLast modified
isa_backplane-1.1-sch.pdf567.9 KiB2016/06/19 02:25
isa_backplane-gerber-1.1.zip394.5 KiB2016/06/19 02:25
isa_backplane-kicad-1.1.zip231.9 KiB2016/06/19 02:25
isa_blackplane-1.1-brd.pdf1.8 MiB2016/06/19 02:25
obsolete_isa_backplane-1.0.zip2.2 MiB2016/06/19 02:26
boards/isa/isa-backplane/start.txt · Last modified: 2023/11/01 17:56 by skiselev
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