Jump to content

[yes, he's insane] A retro computing platform

Recommended Posts

This has been hovering around my mind (and my desk) for quite a time now. Some time in 2012, I had the idea of piecing together a "simple" 8 bit computer from scratch. In late 2012, I discarded my custom discrete CPU design, decided to use a Z80 CPU (8 bit CPU from 1976) instead and started over.


Bread board prototypes have been built, things haven't worked (or suddenly did work for no reason), machine code programs were written by hand, an assembler and a linker have been written, or in other words: yes, he is insane now.


However, today I have hit a critical milestone and decied to tell people about what I've been doing since November. I have a "production quality" prototype on custom etched PCBs and got a simple LED blinking program to work.


Current photo:




Older, but better quality photo (without the chips):




The PCBs, the day after etching:




The very first prototype:




Other than that, this shouldn't be different from any other "rate my PC" thread, so here are some specs:

CPU: Z80 @ 1 MHz clock

ROM: 1 kB boot ROM

RAM: 31 kB in the above setup, extendable up to incredible 8 MB using bank switching

"Mainboard": passive ECB back plane

Memory: audio tape in the near future, no idea how much data it can hold

Graphics: wut? Ahem, I have some plans for abusing an oscilloscope as a vector display in the near future, but a VT220 will be used till then (no graphics). Ideas for a VGA interface are hovering around somewhere.


Sadly it doesn't have any functioning I/O hardware yet. This will receive my full attention now that the finalized basic system design works. Designing and writing an operating system will certainly be fun.


The euphoria is already wearing off. In case anybody is interested in how the project continues, I setup a small blog for my dev-matches.



Share this post

Link to post

10/10 for classic computing!


Compared to almost all other existing computers, -10/10...


I personally like my first rating better. ;)

Don't insult me. I have trained professionals to do that.

Share this post

Link to post

You know you're on a tight budget when your computer case looks like this:



By the way "yay, casing and no flying parts and wires anymore!"

Share this post

Link to post

YAY for homemade cardboard storage and containment systems!

Don't insult me. I have trained professionals to do that.

Share this post

Link to post

Damn, you are going old school. The first system I built was still cruising along at 40Mhz. Or I guess I should more accurately say "assembled" since I wasn't building the PCB boards myself. I did color correct my used CRT monitor though by opening it up and manually fixing the color balance with a screwdriver since it had way too much green.

Share this post

Link to post

I miss those old systems sometimes... Back when it took intelligence just to turn the damn thing on and off without damaging data...

Don't insult me. I have trained professionals to do that.

Share this post

Link to post

This might be interesting:


It's part one of a training video for new employees in the Holmdel Computer Center, showing how a job (e.g. a circuit cimulation or what ever) is processed after handing the punched cards over. (Gotta love the video at least for the sound track^^)


The still picture shows a man inserting a stack of hard drives into an IBM System/370, the same kind I'm wearing here.


Of course, it doesn't show how to boot the system, which requries to temporarily disable the CPU clock and manually keying in the boot loader that reads a bigger boot loader of punched paper strips that than reads an even bigger OS loader from magnetic tape or hard drive that than loads the actual operating system.

Share this post

Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in the community.

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Who's Online   0 Members, 0 Anonymous, 68 Guests (See full list)

    • There are no registered users currently online
  • Create New...

This website uses cookies, as do most websites since the 90s. By using this site, you consent to cookies. We have to say this or we get in trouble. Learn more.