The Microbox II 6809 Single Board Computer

The Microbox II is a 6809 based Single Board Computer (SBC) using the 6883 (74LS783) Synchronous Address Multiplexer (SAM). But, unlike the Color Computer and the Dragon, the Microbox II does not use a 6847 CRT controller -- instead, it uses the NEC 7220A Graphic Display Controller for a resolution of 768x576 -- bleeding edge 1985 technology.

I read about the Microbox II in the December 1985 issue of Electronics Today International. It looked interesting at the time, but there was no way that I could afford it on my first-year-student budget.

In 2002, I met a guy who had ordered and built a Microbox, and still had it lying around. I immediately bought it from him.

This is my Microbox II, in "as received" condition (except that I removed the monitor ROM to read the code, MON09 4.22 20.8.84 (2764, 8K). The one strange thing about the Microbox is that the designer (Dave Rumball / Micro Concepts) did not place mounting holes anywhere on the PCB, so there's no easy way to bolt the PCB to a case. The shape of the PCB also doesn't fit into a modern PC case (the obvious choice, I think) but it does go into an old "AT" style case (the one with the runners for the floppies).

Microbox schematics
Microbox User Notes (36 pages, 630k pdf file).
December 1985 writeup from 68 Micro Journal (1 page, 370k pdf).
December 1985 advertisement from 68 Micro Journal (150k jpg).
March 1986 article from Electronics Today International (3 pages, 214k pdf).

WD 1770 datasheets and information

Information on the WD177x from the BBC Documentation project. (Local copy)
A good copy of the WD177x datasheet from the Commodore archives. (Local mirror)
The WD177x datasheet is also available from the BBC Micro Documentation Project but there seems to be something wrong with the PDF. There's another version available on the Ensoniq pages but the first page is missing. Get the GIFs from the Commodore archives rather.

WD 2123 UART information

It's not easy finding WD2123 information on the web.

2004-12-28 :

Steve Ellenof found this page while looking for the WD2123 datasheet. When he eventually found one, he sent me a copy to post here. So, here's the WD2123 Datasheet, courtesy of Steve.

The Timex / Sinclair FDD3000 used the WD2123 and the WD1770.

"756" Keyboard

Back in the good old days, there was a little shop called the Electronics Supermarket just around the corner from the Greenmarket Square. They sold all kinds of nifty stuph I couldn't afford, I remember they had an AIM 65 on display.

Anyway, I bought an ASCII keyboard from them, model 756C. I have the docs that came with it somewhere, but meanwhile I found a copy here. These keyboards need -12V in addition to the +5V supply, I removed an ethernet DC/DC converter and hacked it onto the site provided on the keyboard PCB.

Of course the Microbox provides -12V on the keyboard connector, I suspect the 756 or keyboards based on the same chip was pretty much standard all over the world for a decade at least.

[Image] Hit Count
hits since 2003-09-29.

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(This page last modified 2003-09-29)