Gigatron Hackers

The Gigatron 512k has a double resolution mode that runs at 12.5Mhz, taking even pixels from one bank and odd pixels at the same address in another bank. This is good for 52 columns using the normal Gigatron font. https://forum.gigatron.io/viewtopic.php?p=2831#p2831 This also works with little cpu i...

Documentation error again :-(. The opcode is $bb. In general, the opcode information in interface-dev.json is the most reliable because this is the source of truth for the c compiler and because the rom compilation process checks that it matches the labels in the rom source. That said, I am happy to...

Correct. I have fixed the doc.

Note that, as of today, EXBA is only used in the microkernel of the multithreading example
https://github.com/lb3361/gigatron-lcc/ ... ff/threads

The callable functions are in threads.h and the kernel in threads.s.

For the standard vCPU instruction set, see "vCPU instruction table" around line 482 of https://github.com/lb3361/gigatron-rom/blob/master/Docs/GCL-language.txt. For compatibility one needs to implement everything that is listed in https://github.com/lb3361/gigatron-rom/blob/master/interfac...

Phibrizzo wrote: ↑24 Feb 2025, 14:38 Why does the MOVIW instruction break the endians rule?

I could not find a way to program MOVIW in 30 cycles (or less) otherwise.

Instruction DOKEI is the same, for the same reason.

BTW I just fixed an error in the vCPU7.md doc. Instruction DOKEI is 35 63, not 35 62.

> And then I asked myself how microcoded CPUs do things. See https://github.com/rafsanofficial/XEROXalto/blob/master/Alto_Hardware_Manual_Aug76.pdf for a well designed example using TTL circuitry. Note the 16 MPC registers implementing 16 prioritized microprogram tasks, with the least priority task ...

I realized that my new way of loading gt1 files is silly. It relies on tracking calls to SYS_Exec to intercept the reset sequence just before executing the main menu. Instead I implant a little piece of code that involves the loader. This is silly because I can just implant the GT1 file we want to l...

Some improvements to http://www.gigatron128k.com The single file box is not only useful to load GT1 files. It can load ROM files and VHD images for emulated SPI SDcards. There are controls to mount and unmount the loaded VHD image on the emulated SPI port. The ability to load any ROM increases a lot...

I just pushed a new version GLCC RELEASE_2.6, accessible via git, with the following changes: Support and examples for the new dev7rom. This version of the compiler will not work with old dev7roms. Use the special branch dev7old for the latest version supporting the old rom if you need to. There is ...

Warning: incompatible changes in dev7rom I just made a bunch of changes in dev7rom that makes it incompatible with earlier versions. Given that there are only a handful of people using it, I believe this is manageable. Just in case, both the https://github.com/lb3361/gigatron-rom and https://github...