Fully-assembled 2SIOR1 boards are now available.

What is it?

A modern version of the MITS 88-2SIO Rev 0 Serial I/O Board used in the ALTAIR 8800 and other S-100 computers. This board provides one or two serial ports using the 68B50 ACIA.This board is functionally equivalent to the original MITS 88-2SIO Rev 0 board but is much easier to configure with switches instead of jumpers, supports baud rates up to 76.8K (great for the Serial Drive Server version of CP/M), has standard DTK/Intel/Crossed RS-232 10-pin IDC headers configured for DTE and DCE, and TXD and RXD status LEDs.

This board comes partially assembled and requires very little soldering. A Bill of Materials is below.

Why did you make it?

I wanted a MITS 88-2SIO configured with switches instead of jumpers and the ability to connect standard IDC-10 to DE9 RS-232 cables.

What makes it special?

This is the first board I designed from scratch.

No Warranty

This board was designed by a hobbyist for fun and is not a commercial product. This board and components come with no warranty or technical support.

Bill of Materials

• 2 - 68B50 ACIA
• 1 - 1488
• 2 - 1489
• 2 - 74LS00
• 1 - 74LS32
• 2 - 75LS85
• 1 - 74LS161
• 2 - 74LS244
• 2 - 74LS393
• 1 - 7805 with Heat Sink
• 1 - 2.2K Resistor Network
• 4 - Bi-color LED (Included with Board)
• 1 - 2.4576 MHz Oscillator (Included with Board)