Motorola 68000 SBC Runs Again With A Raspberry Pi On Top

MC68k SBC with a monitor, keyboard and mouse

Single-board computers have been around a long time: today you might be using a Raspberry Pi, an Arduino, or an ESP32, but three decades ago you might find yourself programming a KIM-1, an Intel SDK-85, or a Motorola 68000 Educational Computer Board. These kind of boards were usually made by processor manufacturers to show off their latest chips and to train engineers who might use these chips in their designs.

[Adam Podstawczyński] found himself trying to operate one of these Motorola ECBs from 1981. This board contains a 68000 CPU (as used in several Macintoshes and Amigas), 32 kB of RAM, and a ROM program called TUTOR. Lacking any keyboard or monitor connections, the only way to communicate with this system is a pair of serial ports. [Adam] decided to make the board more accessible by adding a Raspberry Pi extended with an RS232 Hat. This add-on board comes with two serial ports supporting the +/- 12 V signal levels used in older equipment.

It took several hours of experimenting, debugging, and reading the extensive ECB documentation to set up a reliable connection; as it turns out, the serial ports can operate in different modes depending on the state of the handshake lines. When the Pi’s serial ports were finally set up in the right mode, the old computer started to respond to commands entered in the terminal window. The audio interface, meant for recording programs on tape, proved more difficult to operate reliably, possibly due to deteriorating capacitors. This was not a great issue, because the ECB’s second serial port could also be used to save and load programs directly into its memory.

With the serial connections working, [Adam] then turned to the aesthetics of his setup and decided to make a simple case out of laser-cut acrylic and metal spacers. Custom ribbon cables for the serial ports and an ATX break-out board for power connections completed the project, and the 40-year-old educational computer is now ready to educate its new owner on all the finer points of 68000 programming. In the video (embedded after the break) he shows the whole process of getting the ECB up and running.

[Adam] made a similarly clever setup with a Commodore 64 and an Arduino earlier. [Jeff Tranter] recreated a similar 68000 development board from scratch. And a few years ago we even featured our own custom-built 68k computer.

30 thoughts on “Motorola 68000 SBC Runs Again With A Raspberry Pi On Top

        1. I connect my MEX68KECB to my computer which has 3 RS232 ports. One on the motherboard and two on an expansion card. Of course the thing is now ancient but the old dual core AMD BE2300 is more than fast enough. Every time I think of replacing it I look at the performance difference of current processors and decide that it just isn’t worth losing the serial ports.

          I say MEX68KECB but it is modified. 8MHZ instead of 4MHz, 1MB DRAM instead of 32K, runs CPM-68K, etc.

          Rather than build a case, I found a case at The Container Store. Intended to display cereal boxes for some reason.

        2. My i7 bought in 2016 but I guess new in 2011 has two serial ports, a parallel port, and PS/2.

          I deliberately picked a refurbished that had those ports. I was still using a parallel printer, and my need for serial for a modem was only 4 years in the past.

          Oddly, other than PS/2, I’ve not used the other ports. By the time I moved the printer over, it was a newer one with USB.

          I figure I’ll replace the computer in 3 more years (unless a good deal comes before that) and I may not have the option of serial and parallel ports, but there’ll be even less need.

      1. @Anton Argaiv thanks. I was unable to identify it myself. @epooch: I bought mine at Vintage Computer Fair. I’m guessing it would have been a power connector used in some kind of host machines in college environments; my ECB looked like it was ripped out of such a computer.

        1. I am referring to the one you (and I) bought on eBay. The one you bought at VCF has banana plug jacks on it. BTW, for anyone looking, that style of “banana plug jack” can be found on eBay by adding the part number “101”. That is what I am replacing my molex plug with.

  1. Three decades ago? I got my first KIM-1 in 1976…

    I never did get a 68000 SBC, but did a bunch of assembler on my Macintosh 128. I really loved that instruction set, pick an instruction, pick an address mode and off to the races, it was just so elegant. Not like today’s new fangled gizmos what with all the cache lines and speculative execution and multi-threads and fancy googaws. Get offa my lawn, ya punks! :)

    1. That’s 45 years ago, half decades count too.

      I got my KIM-1 late, in April 1979. 42 years ago. I was reading Byte from the first issue, but didn’t have money for a computer. Someone I knew took an introductory course in microprocessors, and a KIM-1 was part of the package. I didn’t get that one, but the KIM-1 from someone else taking the course, who didn’t want it afterwards. The first surplus microcomputer? Surely among thefirst free used microcomputers.

  2. Quite a long time ago I almost bought a bunch of 68000 boards for dump prices. I think it was early ’90-ies.
    They had an 68000, Eeprom + RAM an Ethernet Interface and and edge connector with I/O.
    They were originally made as a network Interface for some office printer, probably HP.

    1. About thirty years ago, there was an article in Microcornucopia by a guy who’d found a 68010 board, I think industrial surplus. He detailed the process of figuring out what was there, and then putting a monitor in eprom.

      At the time it was so exotic. It didn’t have fancy graphics like the Amiga, but I recall it had more memory.y

      Kids today have it so lucky.

        1. Yeah you got that right!!!!. So many SBCs to choose from with different features, … and ‘small’ … very small. I mean look at the popular RPI PICO with 264K of RAM and 2M Flash… On a 2040 Adafruit Feather, it offers 8M of storage. Then there is the 32bit 133Mhz ‘2’ Core CPU. CPU itself can be bought for $1 ….. So much computing power…. And then you have the RPI 4 itself for only $35… The Arduino class of boards, the ESP6288.. And so on… Yes, us old timers are in a golden age of computing from tiny embedded to desktops/servers. So much power… what to do with it all is the question!!!! Back when I started we were controlling hydro facilities, substations, and such with Z-80 based system at 4-8Mhz and a lot less memory and ROM…. Last board we designed at that company was around the 68332 at a whopping 25Mhz with 1M of SRAM and 1M of Flash….

    2. It sounds like that was an early HP Jet Direct card. It also had a mini-DIN-8 connector to support classic Appletalk. I ended up with a couple of them somewhere. IIRC the EEPROM was a big 40-pin 16-bit monster, and the 68000 was a PLCC package.

  3. > and the 40-year-old educational computer is now ready to educate its new owner on all the finer points of 68000 programming

    author resurrects 40 year old 68000 computer to learn more about 68000 programming – am thinking, gee, that was the CPU that I learned assembly language and C programming on, and developed software for at first job out of university. Time flies

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