Restore 64

Name: Restore 64
Author: Restore 64

A free browser-based Commodore 64 PRG disassembler

Drop any .prg file — packed, crunched, or plain. Restore 64 runs the depacker for real and delivers byte-exact KickAssembler output ready to build. No install. No server.

Open Disassembler →

restore64.asm

.pc = $0810 "Main"
main:
        sei
        lda #$35               // RAM + I/O, ROMs off
        sta CPU_PORT
        lda #$7f
        sta CIA1_INT_CTRL     // disable all CIA1 interrupts
        lda #<irq_0829
        sta HW_IRQ_LO         // set IRQ vector
        lda #>irq_0829
        sta HW_IRQ_HI

Features

370+ Packers — Auto-Depack by Emulation

Doesn't guess the algorithm — runs the depacker as real 6502 code.

Recognizes ByteBoozer, Exomizer, PuCrunch, Time Cruncher, and hundreds more. A full 6502 CPU emulator runs the decompression stub with memory banking, VIC-II raster counter, and CIA timers. Double-crunched? No problem — the emulator keeps running through each stage until the real entry point is reached.

Multi-Phase Analysis

Multiple passes: control flow tracing, IRQ/NMI handler discovery, speculative disassembly, then a second pass to find additional handlers and jump tables in newly discovered code.

Smart Code Analysis

Traces execution from all entry points with register and flag state tracking. Discovers IRQ/NMI handlers, detects self-modifying code, finds inline data, jump tables, and RTS tricks.

Byte-Exact Output — Three Assembler Dialects

Choose your assembler: KickAssembler (v5.25+), ACME, or 64tass. Each dialect gets correct syntax, directives, and addressing mode notation. A built-in verifier reconstructs the machine code byte-by-byte — mismatches are auto-corrected to raw .byte directives. Binary accuracy guaranteed.

Hardware-Aware

Names all 250+ VIC-II, SID, CIA, and zero-page registers. Decodes bitfields in comments so you can see exactly what each hardware write does. Identifies stable raster routines, NOP slides, ROM banking, IRQ vector setup, and other C64 programming idioms.

C64 Idiom Recognition

Annotates common patterns: double IRQ stabilization, CIA interrupt disable sequences, Kernal ROM banking, and raster wait loops.

SID Player Identification

Recognizes 787 known SID player engines from the SIDID database — identifies the exact player and version used (JCH, Vibrants, GoatTracker, and hundreds more).

SID Music Detection

Finds SID music routines automatically — locates init and play addresses using IRQ vector analysis, register write patterns, and call graph tracing. Supports multi-tune programs with confidence scoring and SID data bounds detection.

Syntax Highlighting

Color-coded ASM: labels, mnemonics, registers, numbers, strings, comments, illegal opcodes.

Smart Labeling

sub_ subroutines, irq_ handlers, dat_ data, txt_ strings. Cross-references show who calls what.

PETSCII Strings

Finds text in data regions, formats as .text with correct PETSCII/screencode encoding.

How It Works

Every .prg file goes through a five-stage pipeline. Each stage feeds the next, producing fully annotated, reassemblable output in your assembler dialect of choice.

.prg file

Load & parse header

→

6502 Emulator

Detect & depack

→

Analyzer

Trace & classify

→

Formatter

Emit KickAssembler

→

Verifier

Byte-exact check

→

.asm output

Copy or download

Stage Details

Load — Parses the two-byte PRG load address header and extracts the binary data. Detects BASIC SYS stubs to find the entry point automatically.

Emulator — When a packer is detected, the decompression stub runs as genuine 6502 machine code — no static algorithm analysis, just execution. The emulator tracks every memory write and detects when the real program appears, even through multiple depack stages. Full Kernal and BASIC ROM support, memory banking, VIC-II raster counter, and CIA timers are all included.

Analyzer — Runs in multiple passes. First pass: traces code execution from all entry points (main, IRQ, NMI), discovers interrupt handlers, detects jump tables, RTS tricks, and self-modifying code. Then speculative disassembly scans untraced regions for hidden code blocks. A second pass re-scans for additional IRQ handlers, jump tables, and RTS tricks in newly discovered code. SID music routines are detected and matched against 787 known player signatures. Finally: PETSCII strings, sine tables, charsets, sprite data, and data patterns are classified.

Formatter — Generates KickAssembler-compatible ASM with .pc directives, .const definitions, labeled subroutines, hardware register names, bitfield comments, and C64 idiom annotations.

Verifier — Walks every emitted line, reconstructs the expected bytes, and compares against the original PRG. Any mismatch is auto-corrected to .byte directives, guaranteeing binary accuracy.

Supported Packers 370+ signatures

Restore 64 recognizes 370+ C64 packing, crunching, linking, and protection signatures. When a packed PRG is detected, the built-in 6502 emulator runs the decompression stub and captures the depacked binary for analysis. Multi-stage packing — files crunched twice or more — is handled automatically: the emulator simply keeps going until the original program surfaces.

Packers & Crunchers 284

1001 Card3CodeZipper4c Pack4CodeZipper4WD Soft Packer64er BitKompress64er PackerAbuze CrunchAction PackerAdmiral P4kbarAEB CruncherAEB/CNCD Classic CruncherAgnusAgony PackerALZ64AmigapackerAmnesiaAnticomAntiramApackAutomatic Break SystemBandits Compactor SystemBB BytepressBeastLinkBeefTruckerBeta DynamicBF PackerBit ImploderBit PackerBitPicklerBitstreamerBlackAdderBN 1872Bonanza BrosBongo CruncherBrains PackerBronx PackerBurakiBYG CompactorByteBabyByteBoilerByteBonkerByteBoozerByteBusterByteCompactorByteKillerByterapersByteStrainerC4 Mr.PresidentCadgers PackerCaution HardpackerCaution QuickpackerCCryptCCS BittosCCS ExecuterCCS MaxSCCS PackCCS ScreenCCS SpecCCS SuperComp/EqSeqCCS Triad HackCCS UnknownCeleriPackCharblasterChris Noack Mega-BytepackerCIA CryptCNET FixerCrackman PackCruel CrunchCruncher ABCrush/TabooCult PackerDaliDarkPackerDarkSqueezerDarkSqueezer/DarkfilerDatel UltraCompanderDoynax LZDream PackerDrZoom PackerDSC CruncherDSC PackerECA CompactorEnigma MFFLEntropy PackerEqual Byte CompressorEqualizerExcalibur PackerExcell/Ikari RelocExomizerExpertExploding CruncherExploding FacesFace PackerFalco PackFC3 PackFilecompactor MTBFilecompactor TMC/FPFinal CompactorFinalSuperCompressorFlashCG PackerFlorasoft PackerFrog/BCC e-PackerFront PackerFX BitstreamerFX BytepressG-PackerGalleonGalleon AlvestalinkGalleon ByteraperGalleon CompactorGalleon FW4Gandalf PackerGeneric Sysless $0801Gentlemen PackerGentlemen Stat PackerGimzo/WOWGraf Binaer / F4CG CompactorGraffity PackerGSS COHappy PackerHawk PackerHelmet/TempesTHitmenHuffer/FLTIdiots PackerIkari CrackerILS CompackerInceria PackerISCISC BitstreamISC PackJ0xstrap CruncherJazzcat CruncherJazzcat PackerJEDI PackerJemasoft BasicPackerJewels BytepressJustAPackerKinetic 2KompressMasterKompressMaster/711Koncina PackerKreator PackerKrejzi PackerKress CrunchLameBoozerLevel CrusherLightmizerLoadstar PackerLow CruncherLTS PackerLZMPiMaimerMaktlinkMarauder CruncherMaschinensprache KompressorMaster CompressorMatcham Basic PackerMatcham CharpackMatcham DenserMatcham FlexerMCCracken CobraMCCracken CompressorMCCracken CrushMCCracken CryptMCCracken SCCMCCracken TSSMCCracken TSS IPMCCracken UnknownMDG PackerMeanTeam CrunchMegabyte CruncherMegaCrunchMekkerMrZ PackerMSCrunchMSI CruncherMW PackMW Speedi CruncherNEC PackerNibbitNM156NSU PackerNuCrunchOneway PackerONS PackerOptimusP100Pack64/TabooPacker OptimizerPAN PackerPaninaroPanoramic DesignParadroid PackerPET PackPico PackerPlush ZipperPolonus 101Polonus 4PPolonus EqualizerPridePuCrunchPZW CompactorQRT ProtRap Equal CharsRatt PackRebellic PackerReductorRelaxRows CruncherScreenCrunchSection 8 PackSEEN BytepressShurigen PackSIR CombineSIR MiniPackSledgeHammerSpeedi CompactorSpyPackStarCrunchSubsizerSuper Titlemaker/DSCompwareSupercrunchSuperpackSyncro PackerTaboo CruncherTaboo PackerTAG CruncherTBC MultiCompactorTCS CrunchTDT PackerThundercats PackerTimCrunchTime CruncherTinyCrunchTKC Equal BytepressTLR PackerTotal PackerTrap/Bonzai PackerTrashcanTriad CrackerTrianonTS CrunchTSB PackTSM PackerTurbo PackerUltimate SledgeHammerUltraCompUniPackerUnited Artists PackerUnknown $100 PackerUnknown $101 PackerUnknown $111 PackerUnknown $25 PackerUnknown $439 PackerUnknown $8E PackerUnknown $FD PackerUnknown P3 PackerUProt $0420Uzzy Packer IIVIPVisiomizerWarlock/Panic PackerWCC Modem ConverterWDR Lame KoderWhom PackerX-Rated Exploding CrunchX-Rated Power CrunchX-TerminatorXIPXTC PackerZigag PackerZipLinkZipperZipper/ChromizerZX0

Intro Coders 46

Tools that pack a PRG and prepend an intro/cracktro screen. The depacker handles these like any other packed format.

711 Introdes 3Abyss CoderAEK CoderAllstars CoderBAM CoderBN 1872 IntromakerCFB CoderCobra CoderDD Intro CoderDSC CoderExact CoderExcalibur CoderExcell/Ikari CoderExploding CoderF4CG IntroFDT/AFL CoderFlashCG CoderFLT-01 IntroFP CoderG*P Intro HackHTL CoderICS Drive-8 CoderIkari-06 IntroILS CoderJazoo CoderKGB CoderLST CoderMSI CoderOrion CoderOUG CoderPIT CoderPlasma CoderPowerrun CoderPyra CoderRelax IntroRFO CoderS451-09 IntroSnacky/G*P IntroSPC CoderTAT CoderTFG CoderTFG Pack+CoderTHS CoderTMC CoderTriad IntroTriangle CoderTSM CoderWGI CoderWHO CoderXDS CoderYeti CoderZero/Nato Coder

Linkers 16

File joiners that combine multiple parts into a single PRG, often with compression.

EastlinkerFileLinker/Agony SDAJEDI LinkerLoadstar LinkerLoadstar ModLinkerMarauder LinkerMatcham LinkerMr.Cross LinkerNM156 LinkerParadroid LinkerPSQ-LinkerRatt LinkerSIR MasterLinkerSuper FileLinkerTCD Link CompressorTDT PET Linker

Protectors 12

Code protection and encryption wrappers.

ASC ProtectorChange-ProtectorExprotect/Flash&VoodooFCC ProtectorFlash ProtectorFlashCG ProtectorFlorasoft ProtectorSkylight ProtectorSPC ProtectorStarline ProtectorTLR ProtectorWDR Softprotector

Freeze Cartridge Saves 9

Memory snapshots from Action Replay, Final Cartridge, and other freeze cartridges. Identified but not depacked.

Action ReplayFC FreezeFC1 FreezeFC2 FreezeFC3 FreezeFreeze MachineIsePicStar Expert/Fast FreezeSuper Snapshot

Virus Signatures 5

Known C64 virus signatures. Detected and flagged during analysis.

BHP VirusBoa VirusBula VirusCoder VirusHIV Virus

Documentation

Getting Started

Open the disassembler in any modern browser.
Load a file — drag a .prg file onto the drop zone, or click Load Preset to pick a built-in C64 scene release.
Adjust options (optional) — set entry point, data/code ranges, or comment verbosity in the sidebar.
Click Disassemble — the Analysis Log streams results in real time: packer detection, entry points, IRQ handlers, statistics.
View the output — switch to the Assembly Output tab to see the full KickAssembler ASM with syntax highlighting.
Export — copy to clipboard or download the .asm file.

Options Reference

Option	Default	Description
Entry point	auto	Override the detected start address (hex). Auto-detected from BASIC SYS stub or first code byte.
Data ranges	none	Force address ranges to be treated as data. Example: `C000-CFFF`. Comma-separated.
Code ranges	none	Force address ranges to be treated as code. Example: `1E00-1EFF`.
Comments	Normal	Minimal: SMC refs only. Normal: + hardware names, bitfields, idioms. Verbose: + everything.
Decode illegal opcodes	On	Recognize undocumented 6502 opcodes. Always emitted as `.byte` for KickAssembler compatibility.
Detect PETSCII strings	On	Find and format printable text sequences in data regions as `.text` directives.
Verbose warnings	On	Show detailed warnings in the analysis log.
Auto-depack	On	Automatically detect and depack crunched/packed PRGs via 6502 emulation.
Data blocks at end	On	Group data sections after code in the output for cleaner layout.

Understanding the Output

The ASM output uses standard KickAssembler v5.25+ syntax. Here's what to look for:

// ── Constants ────────────────────────────────────────
.const CPU_PORT      = $01     // CPU port: memory config
.const RASTER        = $d012   // VIC: raster line low byte
.const BORDER_COLOR  = $d020   // VIC: border color

// ── Code $0810-$0860 ─────────────────────────────────
.pc = $0810 "Main"

main:                            // Referenced by: jmp from $0870
        sei
        lda #$35               // RAM + I/O, ROMs off
        sta CPU_PORT
        jsr sub_0840

sub_0840:                        // Referenced by: jsr from $0818
        lda RASTER            // VIC: current raster line
        cmp #$ff
        bne sub_0840           // wait for raster line $ff
        rts

// ── Data $0870-$087F ─────────────────────────────────
.pc = $0870 "Data"

txt_0870:
        .text "HELLO WORLD"
        .byte $00

dat_087C:
        .fill 4, $ff

Labels are auto-generated by type: sub_ (subroutines), irq_ (IRQ handlers), nmi_ (NMI handlers), lbl_ (branch targets), dat_ (data blocks), txt_ (text strings).

Comments include hardware register descriptions, bitfield decoding (e.g. "$D011 bit 3 = 25-row mode"), cross-references ("Referenced by: jsr from $0820"), C64 idiom annotations, and self-modifying code warnings ("!SMC: modified by $0900").

.byte is used for raw data, illegal opcodes (KickAssembler uses different bytes for some), and absolute instructions targeting zero-page addresses (to prevent KickAssembler from optimizing to 2-byte ZP mode).

FAQ

Why are illegal opcodes emitted as .byte instead of mnemonics?

KickAssembler v5.25 uses different opcode bytes for some undocumented 6502 instructions. Emitting them as .byte guarantees the output assembles to the exact same binary.

Why are some absolute instructions emitted as .byte?

When an absolute (3-byte) instruction targets a zero-page address ($00-$FF), KickAssembler optimizes it to the shorter 2-byte ZP addressing mode. This changes the binary output. Using .byte preserves the original 3-byte encoding.

The packer isn't detected. What can I do?

Try disabling "Auto-depack" in the options and setting the entry point manually. Some custom or rare packers may not be in the signature database. The disassembler will still analyze the packed code as-is.

Can I use the output with other assemblers?

The output is KickAssembler-specific (v5.25+). For ACME, ca65, 64tass, or other assemblers, you'll need to adjust directive syntax (.pc → *=, .const → =, etc.).

Is my data uploaded anywhere?

No. Everything runs locally in your browser using pure JavaScript. There is no server, no network requests, no analytics. Your files never leave your machine.

What's the maximum file size?

The practical limit is ~64 KB, which is the C64's full address space. The tool handles files up to 1 MB, but anything larger than 64 KB is unusual for a C64 PRG.

How does the 6502 emulator work for depacking?

The emulator simulates a full 6502 CPU with 64 KB RAM, memory banking ($01 port), VIC-II raster counter, CIA timer interrupts, and ROM visibility. It runs the packer's decompression stub, tracks which memory pages are written, and captures the depacked result when execution reaches the real entry point or enters a raster-wait loop. If the depacked result turns out to be packed again (double crunching), the emulator continues automatically through each stage — no manual intervention needed.