View Full Version : A New S100 Bus V3 MSDOS Support Board

June 4th, 2015, 07:10 PM
I would like to now introduce what will probably be the final version of our very reliable S100 bus “MSDOS Support Board”.

It’s called the V3 MSDOS Support Board. See here:-


(Bottom of the page).

This board has the following additional features:-

1. Added two 22V10 GALs for board port decoding.

2. Add an AT compatible 16550 UART and RS232 driver and port connection

3. Optimize the 8258A Interrupt controller circuit and add a wait state generator (0-8 wait states for INTAs)

4. Correct errors on the AT compatible Timer sound/speaker output. (Ports, jumpers)

5 Added PC style PS/2 mini-DIN connectors for the keyboard and mouse connectors.

6. Add three options for the 5V regulator. A TO-3 LM323K, an EzSBC PSU5 or a Pololu 3A switching regulator.

7. Hand lay down the Vcc line for efficient power distribution on the board.

8. Corrected silk screen labeling of Upper/lower EPROM switches (SW6 & SW10)

8. Silk screen labeled all IC's for easier assembly/debugging.

Much of the heavy lifting on this board was done by Dave Fry (in the UK), thanks Dave.

I will do a group order for a batch of these V3 bare boards. Please let me know ASAP if you would like one or more bare boards. They will run somewhere between $14 - $16 each + shipping.

It’s best to send me an e-mail direct (monahan AT vitasoft DOT org).

This BTW is the last of four in the series of our V3 upgraded boards. These were based on earlier excellent boards that have been upgraded and tweaked over the years. They include the IDE Board, the 16MB RAM board, and the SMB. All were converted over to being GAL based to increase reliability and flexibility.