Commodore 64 Mon Amour(3): disassembling the camel. Reversiamo insieme un gioco del C64 - Agostinelli Ferlito - Codemotion Rome 2018
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In questa terza puntata dedicata al Commodore 64 ci dedichiamo al reverse engineering di AMC e cioè 'Attack of the mutants camels', il classicone sparatutto del grande Jeff Minter pubblicato nel 1983. Smantelleremo insieme il cammello pezzo per pezzo utilizzando le tecniche proprie della pir@teri@ di un tempo (ma usando strumenti moderni), raccontando storie, aneddoti e chicche del codice, rigorosamente assembly del glorioso 6510.
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Commodore 64 Mon Amour(3): disassembling the camel. Reversiamo insieme un gioco del C64 - Agostinelli Ferlito - Codemotion Rome 2018
- 1. Commodore 64 Mon Amour(3): disassembling the camel Andrea Ferlito - Massimiliano Agostinelli ROME 13-14 APRIL 2018
- 2. CIAO – sono ANDREA credits: Marco Giammetti #graziesempre
- 5. <3 <3 <3
- 6. CIAO – sono MASSIMILIANO
- 9. YAK
- 10. GILES
- 13. UNDER THE HOOD: CUSTOM CHIPs
- 14. UNDER THE HOOD: MEMORY MAP 40K 8K 8K 8K
- 15. C64 MEMORY CARD: VIC II 47 registers MEM MAPPED $D000 – $D3FF 53248 – 54271
- 16. VIC II REGISTERS
- 17. C64 SOUND CARD: SID 29 registers MEM MAPPED $D400 – $D7FF 54272 – 55295
- 18. SID REGISTERS
- 19. REVERSING TOOLS • VICE – MONITOR • C64 STUDIO
- 20. REVERSING TOOLS
- 21. 1985 - 1986 TOOLS
- 24. MEMORY CONFIG $0000 $0800 $D000 GAME $E000 $FFFF GAME $A000 $C000 GAME GAMEHESMON SAVE TO DISK SAVE TO DISK
- 25. MEMORY CONFIG $0000 $0800 $D000 GAME $E000 $FFFF GAME $A000 $C000 GAME GAME HESMON SAVE TO DISK $8000
- 26. AMC MEMORY SETUP $0800 BASIC SYS4096 $4000 $2000 $3000 $1000 PROGRAM ENTRY POINT CHAR MAP SPRITES
- 27. AMC VERSIONS • TAP • 5 c=c+1:ifc=2thensys4096 • 10 poke788,52:poke53281,0:poke53280,0:poke53248+24,22:printchr$(8) • 200 load “”,1,1 • D64 • 1983 SYS2061 • PRG • 10 SYS4096 IDENTIFICAZIONE CODICE ORIGINALE
- 28. AMC D64 VERSION
- 29. C64 CHAR AND SCREEN MAP $D018 = %xxxx000x -> charmem is at $0000 $D018 = %xxxx001x -> charmem is at $0800 $D018 = %xxxx010x -> charmem is at $1000 $D018 = %xxxx011x -> charmem is at $1800 $D018 = %xxxx100x -> charmem is at $2000 $D018 = %xxxx101x -> charmem is at $2800 $D018 = %xxxx110x -> charmem is at $3000 $D018 = %xxxx111x -> charmem is at $3800 Character memory Screen memory $D018 = %0000xxxx -> screenmem is at $0000 $D018 = %0001xxxx -> screenmem is at $0400 $D018 = %0010xxxx -> screenmem is at $0800 $D018 = %0011xxxx -> screenmem is at $0c00 $D018 = %0100xxxx -> screenmem is at $1000 $D018 = %0101xxxx -> screenmem is at $1400 $D018 = %0110xxxx -> screenmem is at $1800 $D018 = %0111xxxx -> screenmem is at $1c00 $D018 = %1000xxxx -> screenmem is at $2000 $D018 = %1001xxxx -> screenmem is at $2400 $D018 = %1010xxxx -> screenmem is at $2800 $D018 = %1011xxxx -> screenmem is at $2c00 $D018 = %1100xxxx -> screenmem is at $3000 $D018 = %1101xxxx -> screenmem is at $3400 $D018 = %1110xxxx -> screenmem is at $3800 $D018 = %1111xxxx -> screenmem is at $3c00 $18 = %00011000
- 30. AMC CHARMAP
- 31. AMC SPRITES Sprite pointers $07F8 - $07FF LDA #$80 STA $07F88192/64=128
- 33. DEFENDER
- 34. AMC GLOBAL STRUCTURE • Main Menu Screen • Credits • Players, • Initial zone. • IRQ • Score color cycling • Camel animation • Camel steps sound • Game loop • Spaceship movements • Spaceship bullet • Camel bullet • Scrolling • Radar
- 35. MAIN SCREEN
- 36. MAIN SCREEN
- 37. MAIN MENU
- 38. AMC SOUND ORGANIZATION • VOICE 1, SPACESHIP, BULLET • VOICE 2, CAMEL STEP SOUND, BULLET • VOICE 3, SPACESHIP BULLET HIT CAMEL
- 39. INITIAL SOUND
- 40. SCROLLING CHAR BY CHAR SCROLL
- 47. IRQ FUNCTIONS – SCORE COLOR CYCLING
- 48. IRQ FUNCTIONS – CAMEL ANIM AND SOUND
- 49. JOYSTCK CONTROL CIA 1 and 2 Registers ($DC00 - $DCFF) are repeated every 16 bytes
- 51. SPACESHIP MOVEMENTS Change direction Pressed Right Pressed Left Move spaceship Update sprite X coord Default value $14 = $8F $18 = $A0 – $8F = $11 $14 = $8E $18 = $A0 - $8E = $12
- 52. Thanks! ROME 18-19 MARCH 2016 All pictures belong to their respective authors
- 53. PLEASE SAY NO TO C64 MINI
Editor's Notes
- Wow. She is my wife. Really :D
- So here I am a total idot in love with somthing from the past
- Here in italy we call it Il biscottone
- For English speaker is called Breadbin Don’t know how it’s called elsewhere
- But we re talking about the fantastic Commodore 64
- Let me introduce you Massimiliano. Another old idiot like me. But he is a fucking genius. He used to be a gamedeveloper. He wrote games for c64, c128, amiga, pc and xbox, and nintedo DS. He used to be a pirate, an hacker a security expert. What else… a fucking genius. And for this talk he reversed and commented the entire assembly code of AMC getting it from a binary dump.
- AMC was the first game I ever played on C64, and the first game totally written in assembly on C64 by Jeff. Before AMC Jeff developed ROX 64 that was written in BASIC. This is the tape I bought in 1983, as you can see is not so official. But this was the habit of that time. Sorry Jeff. I can say that I bought it from a very serious company in a very elegant office. They were selling professional Commodore PET computer, VIC 20 and C64 as well and in a hidden corner (not so hidden) they copied games from floppies to tape.
- Now I would like to introduce Jeff and his life philosophy The same philosophy that he puts in their games. I thnk that the best way is to have a look to a couple of pictures of Jeff and Ivan at work
- Or look at Jeff Tweets Probably Jeff is thinking about a new game with of space chickens VS a Giant cock
- And explain which was the inspiration for AMC In the 1982 Empire strikes back for Atari VCS was issued, and Jeff appreciated it, he also loved Defender and there is something similar, Then he look at the review from C&VG they called the walkers "giant mechanical camels“. And he said: I love camels, why not put camels in the game? So this is Jeff (or better my idea about him), the inspiration can come out from anything around him, just few and simple elements, bur very well fitted inside the gameplay. I invite you to try AMC, or other games from Llamasoft, Iridis alpha, tempest or Gridrunner they look so simple. But I can assure you that you cannot stop to play. Every time you start something looks like a bit different, you’ll be totally engaged. I would like to invite Jeff to come on stage and just tell few words about the story of AMC.
- CPU VIC SID CIA Making looking good videogames means to use assembly language sono tutti memory mapped Parliamo di assembly. Il linguaggio permette solo si scrivere numeri in certe locazioni di memoria, fare delle operazioni logico/matemitiche, testare certe condizioni e fare dei salti.
- Brief info about C64 hw architecture VIC e SID E’ tutto memory mapped. Ogni cosa fa rifemimento ad una locazione di memoria. I pixel dello schermo sono in memoria (1kbyte si sposta col banco del VIC insieme ai puntatori agli sprite) I dati dei caratteri e degli sprite ovviamente sono in memoria Non c’e’ harddisk. Il SO (kernal) e le utility sono caricate in ROM sovrapposta alla RAM
- 47 registri MEMORY MAPPED
- 47 registri MEMORY MAPPED
- Curioso l’indirizzamento indiretto indicizzato per fare STA $D018
- Da modificare il commento per la posizione X degli sprite è sbagliato
- Aggiungere il suono nella slide
- SLIDE FINALE
- I banchi del VIC II