ROMulus is a browser-based Commodore 64 KERNAL patcher that lets you customize your boot screen and default colors, plus a few more things. If you have an Ultimate you can drop the kernal right in and replace the stock boot screen with your own design. It’ll also work in VICE or on an EasyFlash with original hardware. It will patch the stock KERNAL or JiffyDOS. It should also work with other KERNALs since it looks for signatures rather than fixed byte offsets.
I finished 1.0 today, and you’re more than welcome to comment with feature requests or other feedback. Enjoy.
- Single HTML file, ~100 KB, no install, no build, no dependencies
- Patches Commodore 64 KERNAL ROM images in the browser — your ROMs never leave the machine
- Boot banner editor (raw PETSCII: color, reverse and cursor codes inside the text)
- Free-memory line and SHIFT+RUN/STOP macro editors
- BASIC READY. prompt editor (needs the BASIC ROM)
- Default border, background and text/cursor colors
- Toggles: LOAD/SAVE default to device 8, boot into lowercase, repeat on all keys, lock the charset
- Floating PETSCII picker — all 128 glyphs drawn from your own character ROM, plus the 16 colors and the control codes
- Enter writes {cr}; Shift+Enter breaks the line for free, so PETSCII art lines up against the 40-column screen without spending bytes
- Live boot preview rendered from your character ROM, with optional CRT shaders (scanlines, curvature, mask, glow)
- Byte budget per text block; refuses to export anything over budget rather than silently shipping the original
- Presets as JSON — share/save settings without sharing ROMs
- Every patch site is found by signature scan, nothing is hardcoded to an address: works with KERNAL rev 1/2/3, SX-64, C64GS, 4064/Educator, Japanese, and JiffyDOS
- Optional one-click fetch of the stock ROMs from VICE’s GitHub, each verified against a SHA-256 fingerprint before it is accepted
- ROMs kept in browser storage for return visits, with a button to clear them
- Round-trip safe: load a patched ROM back in, change nothing, export — byte-identical