Did you ever start a project that you felt gained a life of its own? This project by [Paulo Constantino] is an entire CPU named dreamcatcher on breadboards, and is a beautiful jungle of digital. On top of that, it works to connect to an analog VGA display. How cool is that!
Designing an ALU and then a CPU is a typical exercise for students of digital design and is done using VerilogHDL or VHDL. It involves creating an ALU that can add, subtract etc while a control unit manages data moves and the like. There is also a memory fetch and instruction decode made up of de-mulitiplexers and a bunch of flip-flops that make up registers and flags. They are as complex as they sound if not more.
[Paulo Constantino] went ahead and designed the whole thing in Eagle as a schematic using 74HC logic chips. To build it though instead of a PCB he used breadboards. Everything from bus decoders to controlling an external VGA display is done using jumper wires. We did cover a video on the project a while back, but this update adds a video card interface to the build.
The CPU updates the display buffer on the VGA card, and in the video below shows the slow and steady update. The fact that the jungle of wires can drive a display is awesome. He has since started working on a 16-bit version of the processor and we’d love to see someone take it up a notch.
Thanks to [analog engineer] for the tip.