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S-100 8080 CPU Board Rev 1.
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This board corrects some of the small errors on the earlier Rev 0 board. The main changes are:--
| Added jumpers to be able to create a Memory Write signal without a Front panel (allows board to work stand alone, no need for front panel). |
Single Board Computer Configuration.
Two traces need to be cut if you intend to run this board as a SBC
A new jumper block, JP11, is made of 7 pins in 2 rows as follows:
1 2 3 4
5 6 7
On the top of the board, there are traces that connect pins 2-3 and 6-7.
You will need to cut these traces and either install a jumper block or if you prefer you can just jumper the pads with some wire leads.
The jumper settings for SBC is 1-2, 3-4, 5-6.
If you are using the board as an ALTAIR or IMSAI cpu, with the front panel, then you don't need to cut the traces or install the jumper block.
This jumper reuses a NOR gate to create the Memory Write signal that would have been created by the front panel.
Josh tested the board for SBC use, it work fine, but you may need to apply a reset after power on (there is no power on reset circuit).
If this is important to you, then there are some 3 pin IC's (TO-92) that produce power on reset that can be added.
Step By Step Building the 8080 CPU Board
Steps to build this board are very similar to those of the first (Rev0) board.
The very detailed manual and construction notes for this 8080 Rev 1 board can be downloaded from here.
The files in the zip files below are intended to be placed in the root directory of the onboard SD Memory Card:-
BIOS.HEX – The default Hex file that will be loaded and executed by the ROM Boot Loader.
BOM – Rev1 – Bill of Material to build the card (missing 2 LED’s).
DISK – Images of Single Sided Single Density virtual disks, with CP/M.
JAIR REV1 Schematic – Schematic.
JAIR REV1 Manual – Manual, please read cover to cover.
JAIR-SIO – Serial Interface pin out
MEMMAP – Memory Map of RAM & ROM
Notes
Josh has provided a few more recent update notes for builders of this board.
They can be found here.
More 8080 Monitor Software (AIR-V12.zip) (V1.2 5/15/2016)
More 8080 Monitor Software (AIR-V23.zip) (V2.3 5/18/2016)
Manual and software for the new Rev 1a 8080 board (Rev1a 6/13/2016)
Rev 0 – Released June 5, 2014 (This was the first version of his board).
8080 CPU Board Introduction
JAIR Rev 1d Manual.pdf
Updated manual, schematic and Firmware to v2.4. They are all included in this one file.
Now this board can load disk image files of any defined size. (V2.4 6/26/2016)
Josh has recently fixing the ECO's and has put out a Rev 2 for this board. He now has them in stock.
Here is the Rev 2 Manual and other information about this board (in a .zip file).
SD Card Image and Manual
Other pages describing S-100 hardware and software.
Please click here to continue...
This page was last modified on 06/03/2026