Gigatron Hackers

I agree. The Gigatron and Marcel are a great inspiration. And they are not the only ones that I draw inspiration from. Even the Gigatron includes ideas from other designs. For example, the ALU design did not originate with Marcel and other CPU designs share the same ALU. I think it's which ideas we ...

It's been a long time since I've looked at the Gigatron, but it keeps calling me back. I want to make a version that removes the things I didn't really like about it, but wanted to hear what people here thought. I want a von Neumann architecture so I could do native assembly executing out of RAM (no...

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.

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.

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...

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...

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...

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...

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...

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...