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zig64

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What zig64 is

zig64 is a free, open-source Commodore 64 MOS 6510 emulator core written in Zig. It models documented 6502/6510 instructions and addressing modes with cycle-accurate timing, and aligns CPU cycles with PAL and NTSC timing. Its raster model handles beam behavior and bad lines, but it does not generate video output. For SID analysis, zig64 tracks register writes by cycle and decodes changes such as waveforms and envelopes. Developers can load .prg files into memory for execution, inspect state, follow step-by-step CPU traces, and review SID change logs. Its Asm component decodes instructions into mnemonics and metadata and can disassemble memory ranges. The project can be added as a dependency and imported into a Zig project; the README also describes using Zig’s testing framework to write unit tests for C64 code. It is presented as a base for C64 software analysis, SID player routine inspection, and debugging. The project uses the MIT License, which permits modification and distribution and provides the software without warranty.

Who it suits

zig64 suits developers and enthusiasts working on C64 software analysis, SID player routine inspection, or debugging in Zig projects.

What it does well

  • Cycle-accurate MOS 6502/6510 instruction timing
  • Models PAL and NTSC timing
  • Loads .prg files directly into memory
  • Includes CPU traces, state inspection, and SID logs
  • MIT License permits modification and distribution

What to know first

  • Does not generate video output
  • MIT License provides the software without warranty

Verdict

zig64 provides a focused C64 emulation core with timing, debugging, and SID analysis tools. Its documented scope is analysis and development rather than video output.

Facts from zig64's own pages

Build and tests
The README gives `zig build` and `zig build test` commands; its Requirements heading lists no requirements. · github.com, 5 Oct 2026
CPU emulation
It implements documented MOS 6502/6510 instructions and addressing modes with cycle-accurate timing. · github.com, 11 Oct 2026
Debugging
It provides step-by-step CPU tracing, state inspection, and SID change logging. · github.com, 11 Oct 2026
Disassembler
Its assembly tools decode 6502/6510 instructions into readable mnemonics and metadata, and can disassemble memory ranges. · github.com, 11 Oct 2026
Disassembly
Its Asm component decodes 6502/6510 instructions into mnemonics and metadata and supports disassembly. · github.com, 5 Oct 2026
Headquarters
Vienna, Austria · github.com, 28 Sept 2026
Integration
The README describes zig64 as a computational backbone for virtual C64 applications and names zigreSID as a related tool it can power. · github.com, 11 Oct 2026
Intended users
The README presents the core as a foundation for C64 software analysis, SID player routine analysis, debugging, and custom sound tools. · github.com, 11 Oct 2026
License
The project is released under the MIT License, which the README says allows free modification and distribution. · github.com, 5 Oct 2026
License and warranty
The project uses the MIT License, which provides the software “AS IS” without warranty. · github.com, 11 Oct 2026
Maintainer
The license identifies the copyright holder as Mario Schallner, also known as M64. · github.com, 11 Oct 2026
Maker information
The repository is published by the GitHub account M64GitHub; the opened project page does not state a headquarters or founding date. · github.com, 5 Oct 2026
Maker location
The M64GitHub profile lists Vienna, Austria. · github.com, 11 Oct 2026
Product
zig64 is a Commodore 64 MOS 6510 emulator core implemented in Zig. · github.com, 11 Oct 2026
Program loading
The core can load .prg files into its 64KB memory and optionally set the CPU program counter to the load address. · github.com, 11 Oct 2026
Related project
The README names zigreSID as a related SID sound emulation library for Zig that integrates with zig64 for .sid playback. · github.com, 5 Oct 2026
SID analysis
It tracks SID register writes with cycle information and decodes register changes such as waveform, filter, and envelope settings. · github.com, 11 Oct 2026
Testing
The README describes integration with Zig’s testing framework for writing unit tests for C64 code. · github.com, 5 Oct 2026
Video timing
Its VIC component synchronizes CPU cycles with PAL and NTSC timing and emulates raster events without generating video output. · github.com, 11 Oct 2026
Zig testing
The project describes integration with Zig’s testing framework for writing unit tests for C64 code. · github.com, 11 Oct 2026

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