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Back to the future?

2015
24
December

Back when I was 9 years old I got my first computer, a 48K Oric-1, and it is still in my posession. A couple of months ago I wanted to see if I could build my own replica of it, so I started playing with some components and doing some schematics in Eagle. I wanted a real 6502, RAM, ROM and an AVR to emulate things.

Long story short, and with some routing help from Runar (known from the C64FC project), the boards got done. A couple of weeks later the boards arrived from DirtyPCBs. The board is called "Historic":


The board features a genuine 6502 CPU, 32kb of EPROM and 16kb of RAM. The latter is dual-ported and also interfaced to an ATmega16 which is responsible for rendering the video signals in real-time, as well as feeding the memory with keyboard data.

Unfortunately the board had a couple of critical hardware bugs, they were patched with enameled wire where possible, and a couple of missing components were introduced through a few breakouts.


There! Fixed it.

Here's proof that it works. The Oric ROM boots and accepts user input from the keyboard. This computer is obviously at a very early stage, but it works and can be programmed as long as you stick to the text mode. The ATmega16 will be replaced with a much faster ARM controller later, this will improve the video emulation and open for the other screen modes.

One interesting thing about the Oric is that it uses a 6 pixel wide font. The ATmega16 renders the video using 8-bit SPI. This explains why the font spacing looks a bit funky.


The keyboard is currently interfaced using one of those PS/2-to-UART modules. It gets the job done for now.


It can be programmed, and that's a milestone in itself.

Did I mention this board has an ace up its sleeve? You know, the video generator can pull the video contents from any memory location. This means that we can -- at least theoretically -- run a wide range of different system ROMs.

Here it's running an unmodified Apple II ROM:


Ok, that's all for now, folks! Happy hollidays!

Edit: And now, a VIC-20, too!


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2 Comments

  • Hi Stian. Very nice article and PCB.

    Please tell us which PS/2-to-serial module you're using for the keyboard?

    Regards, Mike

    #924 | Comment by MMcLaren on Jan 28, 2016 12:30am
  • Hi! Thank you for the kind words. The modules I'm using are IC Station branded and were ~$3 a pop, bought from Aliexpress here: http://www.aliexpress.com/item/IC-station-PS2-Keyboard-Driver-Module-PS2-Serial-Port-Transmission-Module/32275298760.html

    #926 | Comment by admin on Jan 30, 2016 05:05pm

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