Search found 21 matches

by alastair
02 Dec 2020, 13:14
Forum: Hardware and software hacking
Topic: List of possible Gigatron mods
Replies: 13
Views: 1937

Re: List of possible Gigatron mods

What's caused the project to stall is actually not getting bored of writing native code - in fact I'm trying to go back to writing native code to re-kindle the enjoyment. Glad to hear it's still ongoing :D I've been working on a similar project to the Gigatron and spent the last year coding in my n...
by alastair
01 Dec 2020, 20:06
Forum: Hardware and software hacking
Topic: List of possible Gigatron mods
Replies: 13
Views: 1937

Re: List of possible Gigatron mods

Add more memory addressing modes -- Most would love to have more addressing modes to simplify coding. This got me thinking. Who else has written (native) code for the Gigatron? Obviously Marcel and there is one other project I'm aware of - https://hackaday.io/project/168293-gigatron-forth Working d...
by alastair
13 Nov 2020, 23:24
Forum: Escape Meta Alt Control Shift
Topic: RCA 1802
Replies: 2
Views: 520

Re: RCA 1802

I started studying the RCA 1802 . I am pretty sure the Gigatron can outrun it, even in vCPU mode. It was a somewhat odd CPU. I worked on a v1802 implementation for a similar project, but switched to a v8080 on Marcel's recommendation :lol: The 1802 is a good fit for a virtual CPU since the overhead...
by alastair
08 Oct 2020, 18:38
Forum: Kit assembly gallery
Topic: Finding parts?
Replies: 17
Views: 3313

Re: Finding parts?

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.
JLC
JLC
Screen Shot 2020-10-08 at 2.34.02 PM.png (245.4 KiB) Viewed 1529 times
by alastair
13 Sep 2020, 12:27
Forum: Hardware and software hacking
Topic: Budgetronics through holes pins for a ZIF socket are too narrow
Replies: 4
Views: 1245

Re: Budgetronics through holes pins for a ZIF socket are too narrow

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...
by alastair
21 Aug 2020, 19:40
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 11079

Re: microtron

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://electronics....
by alastair
19 Aug 2020, 16:48
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 11079

Re: microtron

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...
by alastair
18 Aug 2020, 02:43
Forum: Hardware and software hacking
Topic: Ye Olde Gigatron and Gigatronski
Replies: 11
Views: 2596

Re: Ye Olde Gigatron and Gigatronski

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....
by alastair
04 Aug 2020, 23:19
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 11079

Re: microtron

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...
by alastair
04 Aug 2020, 03:42
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 11079

Re: microtron

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...