Altair 8800 Front Panel For An 8080 Emulator

It appears a very important anniversary passed by recently without anyone realizing. The January 1975 issue of Popular Electronics featured the Altair 8800 on the cover, otherwise known as the blinky box that launched a revolution, the machine that made Microsoft a software powerhouse, and the progenitor of the S-100 bus. The 40-year anniversary of the Altair wasn’t forgotten by [dankar], who built a front panel emulator with the help of some much more modern components.

The build unofficially began with an Intel 8080 emulator written for an Arduino. The 8080 is the brains of the Altair, and while emulators are cool, they don’t have the nerd cred of a panel of switches and LEDs. The hardware began as a bunch of perfboard, but [dankar] wired himself into a corner and decided to make a real schematic and PCB in KiCAD.

Despite the banks of LEDs and switches, there really isn’t much to this front panel. Everything is controlled by shift registers, but there is a small amount of SRAM in the form of an SPI-capable 23LC1024. This comes in handy, because [dankar] is running CP/M 2.2 on this front panel emulator from disk images saved on an SD card. Everything you would want from a computer from 1975 is there; an OS, BASIC, and enough I/O to attach some peripherals.

11 thoughts on “Altair 8800 Front Panel For An 8080 Emulator

  1. Very cool. The 8800 was the very first computer I ever used, and it was still fairly new at the time. It might have been as late as 1977, I’m not sure. I was pretty young then, but I do remember that my father had it hooked up to a terminal rather than attempting to program it from the front panel.
    Interestingly, the fan in that computer made a very unique sound, one I remember to this day and have not heard again since then. I’m not sure why that is, but it does stick out in my memory.

  2. I had two Altair 8800b’s. They were among my first computers too. I *loved* the front panel of the Altair, it was extremely cool. I had mine hooked up to a terminal also. I usually ran one headless and the other with the terminal. One of my Altairs was the “turnkey” model with the 5MB hard drive. Talk about distinct sounds– that 14 inch platter sounded like a jet engine winding up to take off! Sheesh. That was an unforgettable sound! My turnkey Altair also had two floppy drives and I loaded Altair BASIC from floppy. I also implemented CP/M on them later and ran MBASIC.

    In time I upgraded the CPU board to Z80, then Z80A and Z80B for an incredible 4MHz processor speed! And my Z80 board allowed me to upgrade the memory to a whopping 64k. I was living in Dallas at the time and used to go to the local “Hamfests” to swap S100 boards. I eventually got a two port serial board, some more memory boards, and a four-port parallel board. Not all of it was from MITS. I think the parallel board was from Cromemco.

    One of my first robotics projects was using a tank toy chassis and a long cable back to the parallel port of the Altair. I wrote programs to drive it around though it was limited to the length of the wire. Another project I did with it was build a speech synthesizer. That was one of my first wire-wrapped projects. It was an absolute mess but it worked. It was hilarious because it was attached to the serial port and would try to pronounce whatever came out– sometimes I would glom it onto the terminal’s port and when I was in BASIC, it would print out “OK” which the speech synthesizer would pronounce “OCK”. Don’t know why but it always made me laugh. Eventually I got a copy of WordStar running on it which was also pretty cool.

    I had a lot of fun with my Altairs. They were the machines that really taught me about computers and electronics.

  3. Yes, I liked the Imsai also, though I never had one. It was really cool looking. That’s one of the things that modern computers has lost– the blinkenlights and all the whirly bits that made the computers of that era seem like they were something more than a box of chips. IMO, anyway.

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