The latest blog posts.

So for the past few weeks I’ve been building 1 bit registers. And I mean a whole bunch; 32 to be precise. For registers B through E of our 8-bit digital computer. And now I’m starting to wire them together. This is a circuit which implements the entire circuit we described in Introduction to Digital… Read more

A new quick video with a bit of a status update: I now have a working accumulator register tied to my ALU. (I’m also working on the flags register as well as the 4 8-bit registers B through E introduced in the “Introduction to Digital Computers Part 4” video. This includes video of the ALU… Read more

One of the boards I designed simply does not work. Worse, it’s not a simple error: I can’t simply cut one or two lines on the board and run jumpers. Turns out a bunch of resistors were incorrectly wired to power–and cutting them would require so much work it’s easier to basically start over again.… Read more

Why build one when you can build 8, string them together in a primitive card cage and wire wrap the pieces together? This is the accumulator and the ALU together for the first time. I need to build a test circuit and verify the connections before I video tape this part of the work. And… Read more

So it turns out my 1 bit ALU–which has both circuitry for our accumulator and a tristate circuit to write to our bus, works correctly! Over the next week my plan is to assemble 8 of them and hook them up to my ALU. Read more

They’re nowhere near as complicated as the 1 bit ALU boards, but they do contain the accumulator circuit as discussed in our “Introduction to Digital Computers Part 4 video, along with a single tristate circuit for allowing the contents to be written to our bus, as discussed elsewhere in the same video. These accumulator circuits… Read more

One thing about my “Introduction to Digital Computers” series I wanted to verify was that all the circuits designed in the series in fact works correctly. And one aspect of that–which we introduced in the first part of the fourth video–was the complete ALU. While I’ve taken the liberty to do some minor redesigns (so… Read more

Okay, this took much longer than I wanted it to. But finally the fourth video for our Introduction to Digital Computer series! In this fourth video I start to tie the pieces together. We first finish the Arithmetic Logic Unit, then we tie it in with six registers: an accumulator, flag register, and four general… Read more

So here’s where the next video stands. First, as I noted in a previous blog post, I’ve settled on an 8080-like MPU with 6 8-bit registers and an internal 8-bit bus. Now to make an internal 8-bit bus work, you nee a tri-state gate, a logic circuit which can be used to disconnect our logic… Read more

So one of my goals of my series “Introduction To Digital Computers” is to show the design of a computer that can be built entirely out of NPN transistors. The idea is that by showing the design of a digital computer from the absolute ground up–from something you can hold in your hands rather than… Read more

It’s been about a month, and here’s the third video explaining how computers work from the ground up. In this third video I discuss flip flops. Starting with two not gates hooked together I discuss how a bi-stable circuit operates, extend this using NOR gates to Set/Reset flip flops, build data flip flops, edge-triggered data… Read more