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Overview

CPR (Cartridge ROM) files are cartridge images for Amstrad GX-4000 and CPC Plus systems. DevCPC can automatically generate CPR files that boot instantly when inserted.

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What is a CPR?

CPR is the cartridge format for:
  • Amstrad GX-4000 - Console (cartridge-only)
  • CPC 464+ - Computer with cartridge port
  • CPC 6128+ - Computer with cartridge port
Cartridges offer:
  • Instant boot - No loading time
  • Plug & play - Insert and power on
  • Large capacity - Up to 512KB
  • Professional feel - Console-like experience

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Hardware Compatibility

HardwareCompatibleNotes
GX-4000✅ YesConsole (cartridge only)
CPC 464+✅ YesPlus series with cart port
CPC 6128+✅ YesPlus series with cart port
CPC 464/664/6128❌ NoClassic models (no cart port)
Emulators⚠️ SomeRVM, WinAPE (Plus mode)

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Configuration

Add to your devcpc.conf: 
# Enable CPR generation
CPR="${PROJECT_NAME}.cpr"

# File to auto-execute (without 'run' command)
CPR_EXECUTE="loader.bas"

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Simple Configuration

Only specify the filename, not the full command: 
# ✅ Correct - Just the filename
CPR_EXECUTE="loader.bas"
CPR_EXECUTE="8BP0.BIN"
CPR_EXECUTE="disc"

# ❌ Wrong - Don't include 'run'
CPR_EXECUTE='run"loader.bas"'
DevCPC builds the run"..." command automatically.

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CPR Creation Process

During devcpc build, if CPR is configured:

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Step 1: Verify DSK Exists

CPR is generated from the DSK, so DSK must be created first. 
✓ DSK creado: dist/my-game.dsk

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Step 2: Convert DSK to CPR

Uses nocart.py to create cartridge: 
python3 nocart.py dist/my-game.dsk dist/my-game.cpr 'run"loader.bas"'

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Step 3: Patch ROMs

Includes required system ROMs:
  • OS ROM
  • BASIC ROM
  • AMSDOS ROM

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Step 4: Configure Boot

Sets auto-execute command that runs on power-on.

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Step 5: Show Info

Displays cartridge details: 
Archivo:  my-game.cpr
Tamaño:   244K
MD5:      d3d371b683bfe1f988626cdafd8bc132
Ejecuta:  loader.bas
Comando:  run"loader.bas"

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Build Output Example

═══════════════════════════════════════
  Crear Cartucho CPR
═══════════════════════════════════════

ℹ CPR: space-shooter.cpr
ℹ Ubicación: dist/space-shooter.cpr

→ Creando cartucho CPR: space-shooter.cpr
ℹ Archivo: loader.bas
ℹ Comando: run"loader.bas"
✓ Cartucho CPR creado: dist/space-shooter.cpr
ℹ Tamaño: 244K

→ Información del Cartucho CPR:

  Archivo:  space-shooter.cpr
  Tamaño:   244K
  MD5:      a7f8b3c2d4e9f1a6b8c5d2e3f4a5b6c7
  Ejecuta:  loader.bas
  Comando:  run"loader.bas"

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CPR Execute Options

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BASIC Loader

Most common - load BASIC program first: 
CPR_EXECUTE="loader.bas"
The BASIC file can then load and run other files: 
' loader.bas
10 MODE 0
20 LOAD"TITLE.SCN",&C000
30 INK 0,0: INK 1,24
40 MEMORY 23599
50 LOAD"8BP0.BIN"
60 CALL &6B78

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Direct Binary

Load binary directly (no BASIC): 
CPR_EXECUTE="8BP0.BIN"
Binary must auto-start or the screen will just show loading.

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Default Program

Load first program on disk: 
CPR_EXECUTE="disc"
Equivalent to typing RUN"DISC" on CPC.

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Complete Example

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Project Configuration

# devcpc.conf
PROJECT_NAME="mega-game"
BUILD_LEVEL=0

# Paths
ASM_PATH="asm/make_all_mygame.asm"
BASIC_PATH="bas"
LOADER_SCREEN="assets/screen"

# Generate all three formats
DSK="${PROJECT_NAME}.dsk"
CDT="${PROJECT_NAME}.cdt"
CPR="${PROJECT_NAME}.cpr"

# CDT file order
CDT_FILES="loader.bas 8BP0.bin"

# CPR auto-execute
CPR_EXECUTE="loader.bas"

# Emulator settings
RVM_PATH="/Applications/Retro Virtual Machine 2.app/Contents/MacOS/Retro Virtual Machine 2"
CPC_MODEL=6128
RUN_MODE="auto"

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File Structure

mega-game/
├── asm/
│   └── make_all_mygame.asm
├── bas/
│   └── loader.bas
├── assets/
│   └── screen/
│       └── title.png
└── devcpc.conf

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Build Result

devcpc build

# Generated files:
dist/
├── mega-game.dsk  (178KB)  # Disk version
├── mega-game.cdt  (varies) # Tape version  
└── mega-game.cpr  (244KB)  # Cartridge version

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Distribution

Provide users with all formats:
  • mega-game.dsk - For CPC 664/6128, M4 Board, emulators
  • mega-game.cdt - For CPC 464, tape loading
  • mega-game.cpr - For GX-4000, CPC Plus

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CPR Advantages

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For Users

✅ Instant boot - No waiting for tape/disk ✅ No setup - Just insert and play ✅ Authentic feel - Real cartridge experience ✅ Reliable - No loading errors

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For Developers

✅ Professional - Polished distribution ✅ Large capacity - Up to 512KB vs 178KB (DSK) ✅ Copy protection - Harder to pirate than disk ✅ Demo friendly - Perfect for showcases

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CPR Limitations

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Hardware

❌ Not compatible with classic CPC (no cart port) ❌ Requires GX-4000 or Plus models ❌ Can’t modify - ROM is read-only

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Development

❌ Slower testing - Must rebuild CPR each time ❌ No saves - Can’t write back to cartridge ❌ Emulator support - Limited emulator compatibility

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Using CPR Files

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In Emulator

RetroVirtualMachine: 
open "Retro Virtual Machine 2.app" dist/my-game.cpr
WinAPE:
  1. File → Cartridge → Insert Cartridge
  2. Select your .cpr file
  3. System → Reset (CPC Plus mode)

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On Real Hardware

GX-4000:
  1. Flash to cartridge with FlashGordon or similar
  2. Insert cartridge
  3. Power on
CPC Plus:
  1. Flash to cartridge
  2. Insert in cartridge port
  3. Power on or press Reset

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Multi-Format Projects

Generate all formats for maximum compatibility: 
# devcpc.conf
DSK="${PROJECT_NAME}.dsk"    # All CPCs, emulators
CDT="${PROJECT_NAME}.cdt"    # Tape experience
CPR="${PROJECT_NAME}.cpr"    # GX-4000/Plus

CDT_FILES="loader.bas 8BP0.bin"
CPR_EXECUTE="loader.bas"
Build once, distribute everywhere: 
devcpc build

# Test on different formats
devcpc run --dsk    # Test disk version
devcpc run --cdt    # Test tape version
open my-game.cpr    # Test cartridge (emulator)

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Format Comparison

FeatureDSKCDTCPR
SpeedFastSlowInstant
Capacity178KBVariable512KB max
AccessRandomSequentialRandom
BootManual loadRUN"Auto
Hardware664/6128All CPCsGX-4000/Plus
EmulatorsAllAllSome
DevelopmentFastSlowSlow
DistributionCommonRetroProfessional

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Troubleshooting

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CPR Not Created

DSK must exist first: 
# CPR is built FROM DSK
# Ensure DSK builds successfully
Check configuration: 
# Both must be set
CPR="${PROJECT_NAME}.cpr"
CPR_EXECUTE="loader.bas"
Verify nocart.py: 
ls ~/.DevCPC/tools/nocart/nocart.py

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CPR Won’t Boot

Wrong execute file:
  • File must exist on DSK
  • Check filename spelling
  • Use .bas extension for BASIC
Incorrect command:
  • Use filename only, not run"..."
  • Example: loader.bas not run"loader.bas"
ROM issues:
  • Ensure Plus ROMs are available
  • Rebuild with devcpc clean && devcpc build

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Emulator Issues

CPR won’t load:
  • Switch to Plus/GX-4000 mode
  • Some emulators have limited CPR support
  • Try different emulator
Crashes on boot:
  • Check DSK contents are valid
  • Verify auto-execute file works from DSK first
  • Test DSK before building CPR

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Best Practices

  1. Test DSK first - Ensure DSK works before CPR
  2. Simple loaders - Keep CPR_EXECUTE simple
  3. Provide alternatives - Distribute DSK + CDT + CPR
  4. Document requirements - Tell users GX-4000/Plus needed
  5. Use for releases - CPR for final distribution

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Advanced Usage

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Multiple CPR Variants

Create different CPRs from same project: 
# Build normal CPR
devcpc build
cp dist/game.cpr dist/game-full.cpr

# Modify config for demo version
CPR_EXECUTE="demo.bas"
devcpc build
cp dist/game.cpr dist/game-demo.cpr

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Custom Boot Sequence

Create elaborate boot sequences: 
' autoboot.bas
10 MODE 0
20 LOAD"LOGO.SCN",&C000
30 INK 0,0: INK 1,6
40 CALL &BB18  ' Wait for key
50 LOAD"TITLE.SCN",&C000
60 INK 0,0: INK 1,24
70 CALL &BB18
80 MEMORY 23599
90 LOAD"8BP0.BIN"
100 CALL &6B78

CPR_EXECUTE="autoboot.bas"

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Manual CPR Creation

# Create CPR from DSK manually
python3 ~/.DevCPC/tools/nocart/nocart.py \
  dist/my-game.dsk \
  dist/my-game.cpr \
  'run"loader.bas"'

# Verify CPR
ls -lh dist/my-game.cpr
md5 dist/my-game.cpr

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See Also

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