Can anyone identify this S100 serial board?

Richard Cini rich.cini at
Tue Jul 10 21:20:12 CDT 2018

    	The two connectors at the top remind me of the MITS 2SIO board. Chip on the left with the label seems odd — looks like an EPROM. Not sure why they’d use a UART (40-pin chip) and an ACIA, but it’s an interesting two-port combo board. 

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On Tue, Jul 10, 2018 at 10:17 PM -0400, "dwight via cctalk" <cctalk at> wrote:

I'm thinking one serial and one cassette. The 8251 for the cassette.

I can't make out all the chips at the pins? The board was hand laid out. Is there nothing on the bottom but traces?


From: cctalk  on behalf of Ethan via cctalk 
Sent: Tuesday, July 10, 2018 6:43:12 PM
To: cctalk at
Subject: Can anyone identify this S100 serial board?

Trying to identify the S100 serial board in my Imsai 8080.

I assume it was a kit. There are wires from behind one of the ICs that go
to DB25 on the rear, along with other DB25s with a few pins (maybe
cassette input.)

Any help appreciated.

: Ethan O'Toole

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