JC64dis by Ice Team is an advanced, interactive, multi-platform iterative disassembler specifically engineered for reverse engineering Commodore 64 binaries and ROM images. Unlike a standard linear disassembler that blindly converts hex bytes into assembly text, JC64dis allows you to systematically separate code from data in a live, 3-panel iterative workspace. Core Workflow of JC64dis JC64dis processes data across three interconnected panels:
Memory Area (Left): Displays raw hexadecimal bytes (0000 to FFFF). All formatting actions must take place here.
Preview Panel (Center): Displays the real-time disassembly output matching your current memory cursor.
Source Panel (Right): Shows the complete, human-readable layout of the code being generated.
Whenever you apply a change (like naming a label or setting a data type) in the Left Panel, you must trigger a disassembly refresh pass for the tool to re-evaluate the code logic and update the source views. Step-by-Step Guide to Disassembling C64 ROMs 1. File Preparation and Loading
Download your target binary file (e.g., KERNAL, BASIC, or a custom ROM cartridge file like .CRT, .PRG, or a VICE snapshot .VSF). Open JC64dis and load the target file.
If you are mapping raw ROM dumps, specify the correct Starting Memory Address (e.g., \(A000</code> for C64 BASIC or <code>\)E000 for the C64 KERNAL). 2. Differentiating Code from Data
Raw binaries throw text, graphics, data tables, and executable code together, causing basic disassemblers to misinterpret data as broken code instructions. JC64dis solves this interactively:
Identify Code blocks: Select a range of memory in the left panel and define it as CODE. The tool will map MOS 6502 family opcodes instantly.
Identify Data/Tables: If you spot blocks of repeating text characters or zero-sequences (like graphics sprites or sound data), highlight them and flag them as BYTE or WORD data blocks.
Identify Text: C64 ROMs feature dense PETSCII text strings (such as the READY. prompt or BASIC error messages). Mark these segments as TEXT to clean up the assembly display. 3. Resolving Labels and Cross-References
Auto-Labeling: JC64dis automatically assigns standard labels and system constants.
Block Label Wizard: For custom loops or tables, select a range and use the Block Label Wizard to automatically populate uniform labels.
Interactive Navigation: Click on any label in the Right panel to instantly jump to its exact memory location in the Left panel.
Cross-Reference Tooltips: Hover over addresses or registers to view tooltips revealing every other segment of the code that references or writes to that address. 4. Documenting with Comments
Block Comments: Right-click on structural entry points to write large block comments detailing how the following routine functions.
Inline Comments: Attach descriptive side-notes to individual memory addresses or zero-page registers to keep track of variables. 5. Exporting for Reassembly
Once you have fully isolated code from data and named your routines, you can export a clean source file. JC64dis includes optimization presets for major C64 cross-compilers: JC64dis by Ice Team – itch.io
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