Gigatron Hackers

I've just merged Pat's branch into the Gigatron repo , with preservation of its git history. Hopefully I didn't goof up because I forgot how I did it last time. (For future reference, I used instructions from here .) We "promoted" it directly to Utils/lcc/ , even though it's still very muc...

Question for Marcel - when using ALLOC, is $DD a signed integer so that $DD=0x02 increments the stack pointer by 2 and $DD=0xFE decrements it by 2? Correct, because vSP is a single-byte register. Programs typically park values on the stack with these instructions. They were originally squeezed in t...

I was pondering, perhaps it's more efficient to use the vCPU stack as the data stack instead of call stack. We have ALLOC to grow/shrink it by any offset, and we have LDLW and STLW for R/W access at offsets in the stack. The call stack doesn't need these operations. It can be simulated by explicit v...

xora([Y,0]) # AC = XOR(RAM[Y<<8+0],AC) - XOR with the inverted value, so we should end up with zero in RAM (and AC as it also gets stored there too). Is this correct? Almost. xora doesn't write to RAM. Only st can write to RAM. The mem test also tests some/most of the ALU. My 74F board had a shorte...

The mem test tries if it can write to some memory locations. For that you must first know what's there. It also tries to be non-destructive, so at the end of the loop the original value gets written back.

From the source (Core/ROMv3.py): # Simple RAM test and size check by writing to [1<<n] and see if [0] changes. ld(1); C('RAM test and count') label('.countMem0') st([memSize], Y) ld(255) xora([Y,0]) st([Y,0]) # Test if we can change and read back ok st([0]) # Preserve (inverted) memory value in [0] ...

Thanks for benchmarking, and good to see the modified ROM generates a stable video signal that gets accepted. Caveats: Remember that Tiny BASIC was written in GCL which is itself an interpreted language - which suggests two levels of interpretation. C64 BASIC was written in 6502 assembly language an...

You're famous now: https://hackaday.com/2019/04/26/the-no- ... -compiler/

This is an IR image of the 15 MHz configuration running Mandelbrot. I took it to a friend's house, as I don't have a FLIR camera myself. The user registers AC, OUT and Y get warmest. AC warms up to 40 degrees Celsius, OUT slightly above that. For reference, original TTL gets to 60 degrees . Surprisi...

My 74F based build runs at 12.5 MHz now as well: https://youtu.be/VN3eIPT2FUA All 74F logic, except for clock (74HCT04) and input (74HC595) Pull-up resistors in control unit lowered from 2.2kΩ to 680Ω BAT42 signal diodes Removed CLK1-CLK2 delay. The registers didn't update properly otherwise, even w...