Search found 10 matches

by axelb
30 May 2021, 22:50
Forum: Hardware and software hacking
Topic: Video Repeater
Replies: 3
Views: 195

Video Repeater

This is an updated thread for the Gigatron Video Repeater which was already presented in "Possible ways of speeding up the Gigatron". The video repeater is a small add-on board to offload the task of duplicating video lines. Every first line out of four is written to an on-board memory and autonomo...
by axelb
30 May 2021, 08:28
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

@lb3361 Through your "128K expansion" I came across the GAL/PAL, thank you. For understanding the GAL/PAL(CPLD) I still need some time and time is actually my biggest problem. So I have no idea yet if you could still reduce the video accelerator(FIFO) in the chips if you combine both boards. I woul...
by axelb
09 May 2021, 07:15
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

To decouple the VGA clock you would have to regenerate HSYNC and VSYNC. But that would be the minor problem. You would also have to synchronize the Gigatron software with the extension. The Gigatron would have to rewrite the FIFO at the beginning of each new pixel line. For this the Gigatron would ...
by axelb
05 May 2021, 21:29
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

The link below shows at67’s Mandelbrot application with the Gigatron running at about 11 MHz together with my video repeater:
https://youtu.be/yvkT9QpGYkI
by axelb
27 Apr 2021, 12:26
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

Very nice work, thank you. I think I would like to replicate it. I think the PCB clashes with the RAM expander. Maybe I will make one myself. If you intend to add a VGA adapter to your PCB ( following at67´s idea ) there is an example from Ted Yapo on Hackaday. It shows which resistors he used to c...
by axelb
26 Apr 2021, 06:42
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

errata: connection from U3B pin 9 to U4A pin 1 or 2, sorry
by axelb
26 Apr 2021, 06:24
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

[/quote Because this circuit replaces U37 and generates new sync and video signals that still route through the Gigatron's display and input circuitry, (which is very cool BTW), I fear it will not be able to work with overclocked Gigatron's without a re-write of BabelFish and probably using much fas...
by axelb
25 Apr 2021, 12:40
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

To what extent can you use this fifo approach to decouple the VGA timing from the Gigatron clock? Maybe you need two fifos for this. The gigatron fills one at its leisure, while the VGA monitor gets pixels from the other one using its own clock. Then one could speed up the gigatron clock without me...
by axelb
25 Apr 2021, 12:24
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

This is the schematics for my repeater. Currently the "scanlines-off" jumper simply blanks the first out of 4 lines in order to create a "retro look". I tested the board on my Gigatron and it works as expected. However, sometimes i see faint vertical lines between the pixels. I need to check if the ...
by axelb
23 Apr 2021, 19:24
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 32
Views: 1776

Re: Possible ways of speeding up the Gigatron

I designed a small add-on board which can be plugged into U37 output register if the Gigatron has a socket. It writes every fourth line into a fifo memory chip and transmits it back 4 times to the output. By this the Gigatron can be run in mode 1 to 3 still producing an image without blank lines.