PIO 4 Rev-2
The IMSAI PIO 4 Rev-2 is a faithful reproduction of the 1975 PIO parallel I/O board.
The PIO 4-4 contains four independent 8-bit parallel input and output ports.
The output ports may be populated with the included LED lamps to provide visual indications of each bit state.
The PIO 4-4 is also available in a single-port version, the PIO 4-1. Port expansion kits are available to add ports to a PIO 4-1.
One novel feature of the PIO 4 was that is could occupy the first slot in a PCS-80 (IMSAI 8080) chassis and serve as a display-only front panel.
This configuration was never fully supported until now.
Front panel assemblies designed just for this purpose will be available for all IMSAI cabinets currently in the catalog.
When built to the instructions in the new User Manual, the PIO 4 is electrically and mechanically identical to the 1975 IMSAI PIO 4 Rev-2.
The PIO 4 Rev-2 is licensed for sale by IMSAI from RetroTechReboot.
It is entirely produced and shipped by Parastream Technologies.
Complete Kits
Order one from the list below. The kits are complete with everything you need except solder and tools unless otherwise stated.
They even come with a professionally printed user manual.
Please note that the PIO 4 does not come with the connecting cables to the back frame of the cabinet.
Those are purchased separately from the options.
You will need two CABLE B, one for the input ports and one for the output ports.
Be sure to hover over any  icons for more information.
| Description | Part Number | Availability | Unit Price (USD) |
PIO 4-1 Rev-2 complete kit with manual  | PIO 4-1-R | 8/1/2025 | $149.00 |
| PIO 4-4 Rev-2 complete kit with manual | PIO 4-4-R | 8/1/2025 | $229.00 |
Most builders won’t need anything else besides one of the above complete kits.
To skip over the options go to More Information to get links to useful resources.
If you're an advanced builder and want to see all the options, read on.
Bare Board
You may order a bare printed circuit board for you to use your own parts.
Be advised that individual parts are not available to bare board customers unless they are explicitly in the parts list below.
| Description | Part Number | Availability | Unit Price (USD) |
| PIO 4 Rev-2 bare board | PIO 4-R BB | 8/1/2025 | $60.00 |
IMSAI Parts
| Description | Part Number | Availability | Unit Price (USD) |
| PIO 4 Rev-2 user manual | UM-PIO 4-R | 7/15/2025 | $20.00 |
Parts
IC Datasheets
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