Search found 25 matches

by tocksin
30 May 2020, 12:42
Forum: Escape Meta Alt Control Shift
Topic: In memoriam Marcel
Replies: 16
Views: 2758

Re: In memoriam Marcel

I'm sorry to hear about his passing. I've followed his work since before the Gigatron and even tried making my own. I've found its design brilliant. I will miss him.
by tocksin
31 Mar 2020, 12:21
Forum: Hardware and software hacking
Topic: Reading from ROM, LUP and trampolines
Replies: 2
Views: 1821

Re: Reading from ROM, LUP and trampolines

Even though I understood the post-branch instruction execution, I never quite understood the purpose of the trampoline function in the assembler. Thanks for the explanation.
by tocksin
01 Feb 2020, 02:39
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 37
Views: 14155

Re: High resolution mode?

Cleaning up the output with a register is good digital design. I can't seem to find a version that is CMOS and in DIP package and is not obsoleted. I'll keep looking. TTL would probably be ok. Still worst case is two chips, but it's much more slick with one. I'd still like to try the 4063 analog mul...
by tocksin
30 Jan 2020, 21:24
Forum: Hardware and software hacking
Topic: Gigatron optimisation for a lite version?
Replies: 11
Views: 4716

Re: Gigatron optimisation for a lite version?

And because I can't help myself I tried implementing this and it's super simple: 2020-01-30 15_57_30-Control.SchDoc - Altium Designer (19.1.9).png To make this, you'd take the existing PCB and don't populate the ALU or control circuitry. Then add this circuit as a little breadboard on top of it. Jum...
by tocksin
29 Jan 2020, 14:46
Forum: Hardware and software hacking
Topic: Gigatron optimisation for a lite version?
Replies: 11
Views: 4716

Re: Gigatron optimisation for a lite version?

There's still only one databus - A and B is just which table of drivers will be driving the bus. Only one of those 8 drivers will be able to drive the bus at a time, but I don't have enough instruction bits to select all of them all of the time. So for example, I can't choose from the B set of drive...
by tocksin
28 Jan 2020, 16:14
Forum: Hardware and software hacking
Topic: Gigatron optimisation for a lite version?
Replies: 11
Views: 4716

Re: Gigatron optimisation for a lite version?

As a short diversion, I put together a quick datapath and instruction set based on the non-ALU Gigatron. The datapath is basically the same except without the ALU. I added a few extras just for fun - maybe a keyboard, UART, or SPI interface. Dataflow Block Diagram(small).png Also I figure since so m...
by tocksin
24 Jan 2020, 03:15
Forum: Hardware and software hacking
Topic: Gigatron optimisation for a lite version?
Replies: 11
Views: 4716

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: 11
Views: 4716

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: 37
Views: 14155

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: 3242

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...