Gigatron Hackers

JLCPCB is great! I just ordered another revision of my (8" x 5") board plus the expansion card (3.5" square). $30 with FedEx shipping and turned around in 36 hours.

I've had this same issue with a board I designed. I checked the kicad files and the Gigatron is using the standard 0.8mm drill size on the 40-pin DIP. The ZIF socket pins are also 0.8mm, so this can be a problem depending on the tolerances of the PCB. I was able to insert the socket in the first bat...

I'm not sure you're going to find any 74xx461 chips these days. You can still get hold of the 74LS469, but they tend to be expensive. The easiest approach is to "pretend" you are using one of these chips and program a GAL22V10 to look like one (found this discussed on SE below). https://el...

You probably want to look at the 161/163 synchronous counters for doing memory addressing. The 4040 ripple counters have a 35ns propagation delay per flip-flop. The clock needs to transition through 18 stages to get to the MSB in this circuit. This is around 630ns to change from the clock edge which...

The problem with the oscillator might be the resistor values. There is a HUGE difference between getting a CMOS chip and TTL chip to oscillate correctly. It's about 3-orders of magnitude! It takes about 1000x the current to get a TTL chip in to its linear region compared to a CMOS chip (think mA vs....

It makes more requirements on RAM but since is faster than ROM it is easier to make it cope with that The ROM and RAM are used concurrently, so I can only go as fast as the slowest chip. The fastest ROM and RAM chips in the 32-pin DIP package are 55ns, so that's the speed limit. The smaller chips a...

Ciao Alastair! I tryed to search for your schematics but didn't find them. Ciao Steve! I have a project page on Hackaday . There's also a Git Repo with the current build tools. The ALU lookup tables are built with this Ruby script (outputs Intel HEX). It's still a work-in-progress, but I hope to ha...

Active adapters normally have 2 PS/2 plugs (keyboard/mouse) that connect to a little black box with cables. https://m.media-amazon.com/images/I/51bP7iuibGL._AC_UY436_QL65_.jpg The image shown is going the other way (PS/2 to USB). This converter allows a PS/2 keyboard and mouse to a connect to a sin...

It's a non trivial undertaking that you have set yourself upon and a truly formidable firmware update. I started a similar TTL computer project 16 months ago. The hardware is done and working great, but most of that time has been working on the firmware. I'm about a year in and just starting to see...

I have the same programmer for my project. I started with the Windows software and entered machine code programs directly in hex! That was pretty painful, so I developed some automated tools. I have a build script that runs on my MacBook and calls minipro to burn the ROM image. The specific command ...