The Altair 680 was announced in the November 1975 issue of Popular Computing, just 10 months after the seminal Altair 8800 was announced. The machines were supposed to ship in January 1976, but hardware design problems delayed shipment until May. In the meantime, Bill Gates had a high school friend rewrite the 8080 version of BASIC to work with the new processor.

The 680 was intended to be a lower power, more affordable version of the 8800. But in reality, the Motorola 6800 processor was every bit as capable as the Intel 8080 (when running at 1MHz). In order to have the appearance of being a cheaper computer MITS made the marketing decision to slow down the processor to 500kHz, and to "dumb-down" the front panel making it more difficult to program from the toggles.

Instead, the 680 included a 256-byte monitor ROM that enabled the user to enter machine language code from a keyboard, whether that was from a Teletype or a new-fangled (and quite expensive) "glass terminal". The 680 supported a paper tape device for loading and storing programs, and MITS eventually released a cassette interface. A disk drive option was planned for the 680, but that project was shelved during the Pertec takeover of MITS in late 1976.

While the front panel may be hobbled, it still looks great with the toggles and the blinkenlights. Shortly after I made my first Altair-Duino 8800 in 2017 I knew I'd have to follow it up with my version of the 680. It's a much easier build than the 8800 but still plenty of fun, and it fits great on a shelf or on your desk to spark conversation.

My initial offering of the Altair 680 Arduino Due-based emulator is designed to use a commonly available project case. The kit I am selling does not include the case, but you can easily find them on Amazon, eBay, Ali Express, or many other sources for electronic components. The case is often called the “Fielect Metal Project Case” or sometimes just the “Blue Metal Project Case” but the one you want always has the dimensions of 250mm x 190mm x 110mm (or 9.84” x 7.48” x 4.33”).

What you will receive is a professionally made custom circuit board, an Arduino Due compatible, all through-hole components, and all the toggles, LEDs and the rest of the bits you'll need to get your Altair-Duino up and running.

The Altair-Duino 680 includes built-in Altair 680 Cassette BASIC v1.1, VTL-2 (Very Tiny Language), and the MITS Assembler/Editor v1.0. CSAVE and CLOAD in Cassette BASIC utilize the built-in SD card for storage, and some programs are included on the SD card ready to load.

You can connect to a laptop/desktop via a USB connection and use terminal emulator software like PuTTY, Tera Term (or Serial 2 for Mac). The Altair-Duino 680 also features a DB9 serial port for connection to a real serial terminal.

A more realistic-looking Altair-Duino 680 Pro will be coming soon. I am working with a manufacturer to create a replica of the original Optima case and front panel (please note: this current version of the kit will not fit in the full-size reproduction case).