Simple CPU - University of York Apr 04, 2018Figure 1 : Simple CPU. Modern CPU's are complex beasts, highly optimised and tricky to understand. This makes it very difficult to see why it was constructed in the way it was. Part of the problem is the requirement for backwards compatibility i.e. a new processor has to be able to run code from the previous generations. Custom 4-Bit CPU Schematic and Control | Big Mess o' Wires Custom 4-Bit CPU Schematic and Control . August 27th, 2013 | Category: Nibbler. Enough with the vague design talk – here’s the circuit schematic for the Nibbler 4-bit CPU! Click the image to zoom in to a full size view. – Make a super-simple example of a 7400 CPU doing interesting stuff – Make the most powerful 7400 CPU possible.