Ben Eater 8-Bit PC

[PaulKappmeyer]

I’ve watched Ben Eaters 8-Bit computer series (yt: here) and built his computer in Digital.

Since Digital already provides all the need 74xx ICs, it was very easy and fun to follow along. So, I wanted to share the result.
At first, I wanted to follow the built very strict meaning that the layout and connections should look like shown in the videos. So, I used every chip that was used in the video. This could be a bit inefficient, for example when just one inverter is used on a hex-inverter IC.
Also, the wiring became a mess in the end (see first picture), which is way I decided to tweak the final build and share multiple versions. I have packed 4 Dig-Files and attached the ZIP-File at the end.

Afterwards you can find some explanations to the versions:

• 8-Bit PC 00:

This is the very complete version with every wire drawn out almost identical to the original.

• 8-Bit PC 01:

This version uses splitters/mergers to make the bus connections and also tunnels on inputs and outputs to make the whole circuit more compact

• 8-Bit PC 02:

Even more tunnels are used to make the circuit more compact. And some basic logic ICs are replaced with the Digital gates to make their function clearer.

Program memory:
The video series uses two 74189 ICs (64-Bit RAM, 16word 4-bit) as its program memory. DIP switches are used for manual programming. Anyway, this manual programming can get really annoying and exhausting. To be able to program the computer (a bit) easier, I slightly modified the 74189-chip, so that it now uses and EEPROM. This ROM can then be edited trough the ‘Content of ROMs’ menu.

• 8-Bit PC 03:

This version is the transmission of Ben Eaters PC to Digital without using the 74xx ICs. Instead, all functionality is provided by Digitals built-in components. This circuit is much more compact while containing the layout and functionality shown in the series.
Program memory:
A RAM component with the ‘Program memory’-option set is used as program memory. I’ve attached a hex file of a simple program, which counts to 255 and back down to 0. This file can be integrated to the preload option in the ‘Circuit specific settings’.

Here you can find all the Dig-Files and also the hex-File with the basic program:
Ben_Eater_8_Bit_PC.zip

[ghost]

Nice! I just started the video series and was about to start down the same path.