Search found 19 matches

by tocksin
24 Jan 2020, 03:15
Forum: Hardware and software hacking
Topic: Gigatron optimisation for a lite version?
Replies: 7
Views: 148

Re: Gigatron optimisation for a lite version?

Well, I wasn't thinking of adding another ROM, but just using the program ROM. All it takes is 256 byte table to do an increment. Then use an indexed load to get the new value. But the philosophy is still the same - where do you want to do your calculating? I guess my preference is to figure out the...
by tocksin
23 Jan 2020, 21:08
Forum: Hardware and software hacking
Topic: Gigatron optimisation for a lite version?
Replies: 7
Views: 148

Gigatron optimisation for a lite version?

I've been reading about some other CPU designs, and came across one which has no ALU, but does arithmetic via ROM look-up tables. It only does a 8-bit increment and decrement, but proves that any arithmetic function can be supported with those two functions (and technically only increment). Addition...
by tocksin
03 Jul 2019, 20:32
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 33
Views: 4373

Re: High resolution mode?

This is all amazing work guys. I love when it comes together. Seems like the inverter in the '157 is causing the problem; however, we already have the inverse of this signal - the opposite clock signal. So we really only need the AND/OR logic to do the multiplexing. With 6 AND and 3 OR gates, you'd ...
by tocksin
22 Oct 2018, 19:52
Forum: Hardware and software hacking
Topic: First gigatron clone
Replies: 11
Views: 2153

Re: First gigatron clone

The audio IN right now is a simple band-pass filter / amplifier. It's only for digital input from an audio source. It should ramp the output up to the point where the CMOS chip can read either a high or low. The software will need to read one bit at a time. It won't be fast, but I'm ok with that for...
by tocksin
19 Oct 2018, 13:56
Forum: Hardware and software hacking
Topic: First gigatron clone
Replies: 11
Views: 2153

Re: First gigatron clone

Boards are in! They look good on first inspection. Time to start building and testing. Thanks guys for the coupon!
IMG_2883.JPG
IMG_2883.JPG (901.57 KiB) Viewed 1560 times
by tocksin
27 Sep 2018, 17:00
Forum: Hardware and software hacking
Topic: First gigatron clone
Replies: 11
Views: 2153

Re: First gigatron clone

I made a quick cartridge example so I could make sure I didn't make any mistakes with the wiring. Turned out a lot bigger than I expected. I could probably make it smaller with surface mount chips...
2018-09-27 12_58_43-GGTcart.PrjPCB - Altium Designer (18.1.9).jpg
2018-09-27 12_58_43-GGTcart.PrjPCB - Altium Designer (18.1.9).jpg (30.46 KiB) Viewed 1690 times
by tocksin
21 Sep 2018, 14:01
Forum: Hardware and software hacking
Topic: Extending the Gigatron instruction set
Replies: 22
Views: 3331

Re: Extending the Gigatron instruction set

My new logic only requires a single extra (4x)OR chip, and I'd rather not have to add another chip. But I think I've figured out a way to have the override to select D on the lower byte without more chips. The problem is that I need an inverter and I don't have one. But I can have effectively an inv...
by tocksin
20 Sep 2018, 15:00
Forum: Hardware and software hacking
Topic: Extending the Gigatron instruction set
Replies: 22
Views: 3331

Re: Extending the Gigatron instruction set

If the diode logic is really causing that much of a slow down, you could decrease the value of the pull-up resistors. It would consume a lot more current, but that might be a easy tradeoff for speed.
by tocksin
19 Sep 2018, 13:44
Forum: Hardware and software hacking
Topic: Extending the Gigatron instruction set
Replies: 22
Views: 3331

Re: Extending the Gigatron instruction set

I like this idea. This would change the ST AC -> [X++, X++] instruction to ST AC -> [X++, D] which is much more useful. More instructions for no more chips is good!
by tocksin
18 Sep 2018, 16:05
Forum: Hardware and software hacking
Topic: All-In-One DB9
Replies: 5
Views: 769

Re: All-In-One DB9

You could have a one cable that splits out into the multiple connectors. Or have the cables in a cable wrap, so it looks like one cable. Like this:

https://www.parts-express.com/parts-exp ... k--080-558