Search found 23 matches

by tocksin
21 Sep 2018, 14:01
Forum: Hardware and software hacking
Topic: Extending the Gigatron instruction set
Replies: 22
Views: 3433

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: 3433

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: 3433

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: 793

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
by tocksin
15 Sep 2018, 11:57
Forum: Hardware and software hacking
Topic: First gigatron clone
Replies: 11
Views: 2237

Re: First gigatron clone

I took the store instructions which read and write to/from RAM, and replaced them since they were useless. I kept all the others. Instead those instructions now read from the AC register and then select X as the upper byte (when 0 is not selected). The only really useful one is ST X,D, but there is ...
by tocksin
14 Sep 2018, 19:51
Forum: Hardware and software hacking
Topic: First gigatron clone
Replies: 11
Views: 2237

First gigatron clone

I don't mean to step on any toes, but I couldn't wait for a Gigatron with a built-in keyboard, so I'm making one myself. The Apple had tons of clones, so it makes sense the Gigatron should have one too. Mechanical keyboards is also a hobby of mine, so I wanted to combine the Gigatron with one. I use...
by tocksin
28 Aug 2018, 19:43
Forum: Hardware and software hacking
Topic: Audio storage of programs
Replies: 1
Views: 465

Audio storage of programs

With the creation of BASIC, I'm thinking of ways to store and load programs. I'd like to be independent of another computer. I think the best medium is something we have on hand these days - our smart phones. We could do what retrocomputers did and use audio medium to store and load programs. We hav...
by tocksin
15 Aug 2018, 20:08
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 34
Views: 4683

Re: High resolution mode?

I wonder if a 74HCT14 would oscillate closer to 50/50 duty cycle. It's still an inverter, but has Schmitt triggered inputs. If you haven't tried it, I will get some and see if there's any improvement.
by tocksin
14 Jul 2018, 20:48
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 34
Views: 4683

Re: High resolution mode?

I'm thinking to get both the high-res and low-res modes, we could add a 2:1 analog multiplexer: 74HCT4053. We'd need two different resistor arrays, but this would be a simple solution. Then we could pull a line from the blinkenlights to the select line. OR as a more advanced option - we could captur...
by tocksin
13 Jul 2018, 13:58
Forum: Hardware and software hacking
Topic: Extending the Gigatron instruction set
Replies: 22
Views: 3433

Re: Extending the Gigatron instruction set

What about something a little less intrusive? I'd hate to become incompatible with the current instruction set with all of the work people are doing developing the software. What if we just replace the instructions which are currently unusable? Specifically, the store instructions which write to RAM...