33. C128D and the MITS Altair: Best Friends Forever

Now that old Hank has earned your trust with these 30 or so episodes, it's time to dish out a little secret: Commodore will always be #1, but you can bet your bottom dollar that there are  a whole lot of cool computers available from other companies as well! On top of that, some of them are even older, more obscure, and harder to use than the C64! Let's talk about one of my favorites and see how it fits into computing history.

The MITS Altair 8800a is widely considered as the first successful home computer (sorry Kenbak-1) and gained the attention of hobbyists through a January 1975 cover article in Popular Electronics magazine. Originally sold in kit form for $439 US by a company heretofore known for selling model rocketry supplies, the system paired the Intel 8080 CPU with a spacious 256 bytes of RAM. Input and output was handled through a set of data/address toggle switches and LEDs, respectively. Despite these technical limitations, hardware and software engineers soon created a cottage industry from expanding the Altair's repertoire, be it adding disk and hard drives, paper tape readers, expanding the amount of available RAM, finding ways to play sound from the computer, or porting a variety of operating systems, games, productivity applications, and programming languages to the computer (Microsoft saw its beginnings in developing the version of BASIC used by the computer). Though MITS itself was sold within a couple of years of the Altair's release and the computer was supplanted by "friendlier" home computers such as the Apple II and Commodore PET, the Altair is still remembered fondly by many early home computer enthusiasts.

Working with an Altair 8800a in the modern era is a little more tricky. The kit was famously difficult to build for many electronics neophytes, was quite bulky (~65lbs) and prone to failure (a property which certainly hasn't lessened with age), and, like many sought-after vintage computers, is extremely rare and pricey nowadays. Thus, the difficulty of finding and working on the original equipment has driven modern hobbyists to more convenient and cost-effective solutions. Enter the Altairduino by Famous Davis LLC: a sleek, low-priced, Arduino microcontroller-based scale reproduction of the Altair 8800a, eschewing the antiquated S100 bus and hulking original power supply. In their place, we instead get a 26-pin expansion bus, built-in floppy and hard disk emulators, the ability to connect a USB keyboard and VGA monitor, and a DB-9 serial interface allowing end users to interface a traditional teletype terminal. It's this third option that we'll be using when we control the Altair via a more-friendly-and-familiar home computer.



Wait, did I mention I built one of these things? Yeah, I built one of these things.





I don't have a ton to say about the build itself - it took a few days, was fairly simple to complete (due to a nice step-by-step build guide and some welcome advice on how to mount banks of switches and LEDs evenly), and resulted in a reliable, well-engineered product that also looks really nice on my desk.

Now that we know about the Altairduino, let's take a step forward to the 1980s and shuffle our way over to the world of Commodore. At this point, I'll introduce you to another piece of hardware that'll allow us to connect a C64 or C128 user port to a device like the Altairduino that uses a DB-9 connector. The GLink LT is a user-port-to-DB-9 RS232 serial interface adapter that supports both VIC-1011A and UP9600 communication modes allowing for speeds up to 9600 baud. (The VIC-1011A was Commodore's original answer to RS-232 serial connectivity in the 1980s and used a non-standard edge connector instead of the more universal DB-9 plug now in wide use). The GLink also adds a couple of modern niceties such as a 5V IEC header allowing users to draw DC power from the user port in order to daisy-chain an additional device like a SD2IEC.

We'll next need a terminal emulator program to run on the Chorkin-approved Commodore 128D. I chose Desterm, which we last used all the way back in Episode 6, "Online with the C64 Wifi Modem". Desterm supports the GLink LT adapter and makes use of the C128's 80 column mode to give us a more usable and modern screen width (many systems expect 80 columns in particular, though many C64 BBS interfaces were designed with the computer's 40-column limitation in mind).



We connect the GLink to the C128Ds's user port, run a DB-9 cable from the Commodore to the Altair (the Altair's end is "DCE", meaning no null-modem cables or adapters are necessary), and we load and run Desterm. This application requires a couple of setting changes to accommodate the GLink, so we'll set the serial mode to "Cheap RS232" and change the baud rate to 9600bps in our Protocol Settings menu.

Time to boot up the Altair! We're loading communications profile #2, so we set switch SW1 up (binary for "2") and hold the "Deposit" momentary toggle upward while we power the computer on. Toggling AUX1 down them gives us a menu of several pre-loaded Altair OSes and applications. Among the available selections are the "Kill the Bit" switch-and-LED game, a calculator program, a LED version of Pong, or we can make the computer sing "Daisy" (you may think this is an oddly specific request, to which I say "look it up"). There are options for 4K and 16K ROM BASIC, but I'd assume most Commodore users have already had their fill of that particular programming language by this point.



Let's dig a little deeper and load Zork from disk! Beyond the menu items mentioned above, the Altairduino also includes a selection of unlisted disk images that are mounted using the front panel switches. Our Zork disk uses switches 3 and 12 up, with all others down. Toggle AUX2 down to load the disk, then flick switch 12 down and toggle AUX1 down to install the disk boot ROM and boot from drive 0. You'll land at a familiar "A>" prompt - type ZORK1, hit Enter, and I'm fairly certain you'll soon find yourself in an open field west of a white house with a mailbox nearby.



It's a shame that I probably won't write much more about the Altairduino on this website. I've only started to scratch the surface of the software bundled with this computer, but I also didn't want to go on for another ten paragraphs when I'm supposed to be spending my time focusing on the Commodore ecosystem. Instead, I will strongly recommend you explore some of the Altair's rich history and consider building one of these machines for yourself. Nothing comes from nothing, after all, and a bit more ancestral computing knowledge under the belt never hurt anyone.

This site is copyright 2023 Hank Wesley Chorkin. If you don't like it, you can get out!

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