Search found 400 matches

by marcelk
01 Dec 2019, 22:38
Forum: Hardware and software hacking
Topic: Cosine
Replies: 0
Views: 73

Cosine

My favourite method to do cosines and sines with just integer math. 'Plot cosine 10 cls 20 input p:if p<1 goto 20 30 u=50*100:v=0:c=0 40 for x=0 to 159 50 y=68-u/100 60 poke y*256+x,c 70 u=u+v:v=v-u/p 80 next x 90 c=c+23:goto 40 Cosine.jpeg It's stable in the sense that it seems to maintain its ampl...
by marcelk
01 Dec 2019, 18:31
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 80
Views: 8624

Re: Expansion bus

I just found and fixed the issue in CardTest.gcl. It turned out to be a one-character typo that has always been in there. Depending on where the file is placed it may or may not trigger. The current revision walks through the root directory and lists the entries it finds. Once it sees BOOT.GT1 it st...
by marcelk
28 Nov 2019, 19:42
Forum: Hardware and software hacking
Topic: Pluggy Reloaded
Replies: 33
Views: 1170

Re: Pluggy Reloaded

Mine arrived today. I couldn't postpone the build until the weekend, so here we are. It works! Great job! PluggyReloaded.jpeg I decided to have the female connector for the breakouts, so I desoldered the pins from the SDC board and swapped connectors. That took most of the build time. Heating up the...
by marcelk
24 Nov 2019, 04:35
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 31
Views: 1286

Re: Modified Gigatron Design Ideas

The '244 is just a tri-state buffer, not a register, not even a latch. You can find a really good explanation here . This video is part of the Ben Eater youtube series that goes through all steps of building an 8-bit breadboard computer. It is a very good resource for you as well. There are 44 video...
by marcelk
24 Nov 2019, 00:48
Forum: Hardware and software hacking
Topic: A Forth for Gigatron?
Replies: 9
Views: 793

Re: A Forth for Gigatron?

Your HaD logs and GitHub commit messages are super enjoyable to read. You made fantastic progress and it looks well under control. Actually, I believe you've cleared the biggest obstacles already. The ability to fetch threads from ROM is super cool. I struggle to achieve the same for vCPU. Very impr...
by marcelk
24 Nov 2019, 00:35
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 31
Views: 1286

Re: Modified Gigatron Design Ideas

I believe my proposal is sound. The data sheet for the XOUT chip is here here. I'll leave it at that.
by marcelk
23 Nov 2019, 22:29
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 31
Views: 1286

Re: Modified Gigatron Design Ideas

For understanding the 8-bit architecture, I suggest to watch Walter's talk (and slides) on the Gigatron's site front page, browse our data sheets page, check the annotations in the instruction decoder schematics, or study the mini emulator Docs/gtemu.c. The latter acts as the definitive instruction ...
by marcelk
23 Nov 2019, 09:27
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 80
Views: 8624

Re: Expansion bus

Before I start soldering, I wanted to confirm that the tweaked resistor values and bodge wires documented in https://forum.gigatron.io/viewtopic.php?f=4&t=64&start=50#p804 are still the most current game plan as far as h/w side goes? That is correct. On the software side, some heads-up: Between ROM...
by marcelk
23 Nov 2019, 00:40
Forum: Hardware and software hacking
Topic: Help to understand src rom code
Replies: 4
Views: 175

Re: Help to understand src rom code

This is of course the first native assembly routine that people encounter, and they may not have watched one of Walter's Gigatron lectures. Only at the third branch instruction the delay slot is really important. So better point it out in the comments. I just updated this in GitHub. The memory count...
by marcelk
22 Nov 2019, 23:03
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 31
Views: 1286

Re: Modified Gigatron Design Ideas

I am not understanding why you are having difficulty following. I will try again. I asked if the syncs from the 2nd Gigatron in this arrangement (the one you put on the left) could be used to drive the keyboard shift register on the first one (the one you put on the right)? Thus you wouldn't need t...