BAM!BAM!BAM!
BAM!
BAM! BLUE AZURE MONDAY BAM!
BAM!
BAM!BAM!BAM!BAM!
GALAGA is next in the series of about 10 originals on the Atari 7800. It was a huge hit when it burst into arcades in 1981. It was a sequel to 1979's GALAXIAN, which also spawned several sequels of its own, is an intense space shooter. In 1984 this was to be the 7800's answer to the 5200's GALAXIAN.
DISASSEMBLY NOTES (true for all disassemblies)…
Thus far, not a single Atari 7800 .asm file has matched the corresponding released binary 100%. This isn't a surprise, nor a bad reflection of the engineers involved. We know there was a gap between the original designs of ca.1983-1984 and the eventual release of ca.1986. This was a period of unknown potential design changes at Atari, and the changes aren't documented as far as we know. The carts were released and they work, as they work. The original cart designs have been frozen for decades, never-ever reviewed in detail as they are now. To locate the differences between the released source list and the released binary, simply open the disassembly .rtf file and do a text search for "source" (without the quotes) and you'll see red text highlighting the differences. The green text is program comments and disassembly comments are in black. It's that simple. And whenever I see a typo error I clean those up as well. "Missle" should be spelled Missile, and now it is.
GALAGA Disassembly…
Image may be NSFW.
Clik here to view.
GalagaDisassembly6.rtf 475.83K
12 downloads
(CAUTION: This is over 200 pages).
DEVELOPMENT OF GALAGA-14…
GALAGA was another fave of mine in the late 1980s. At first I was avoiding the macro-beams deployed by the Galagan Flagships, only to find out this is the way to get dual ships, but you have to follow the instructions (see the user's manual). Before developing my custom GALAGA game, I was thinking of naming my custom game GALAGAGA, but then I thought of Lady Gaga, which immediately changed my mind. To retain the look & feel of the original GALAGA game, I tended avoid creating invincibility for this game. Results of testing the changing of the start # of lives count with the ProSystem Emulator 1.3 (and confirmed on the 7800 hardware):
If the game starts with over 36 (24 hex) lives, the game crashes. If the game starts with over 20 (14 hex) lives, the game won't display the level number. The game will display up to 14 (0E hex) ships, so that's what we start with. This way, at the first death you will see a ship lost. Hence the name GALAGA-14. At first it may be disconcerning to see all these ships along the bottom, but this means more lives and more game time to achieve higher levels. Without more modification, no 99 lives or invincibility is immediately available. The game does offer some amazing opportunities for modifications I hope to build later, when more time is available.
HOW IT WAS DONE...
Looking at the disassembled code:
ATITOUT:
8290 A9 04 LDA #$04
8292 85 B1 STA LIVES
8294 AE 23 27 LDX TWOPLAYR
8297 F0 02 BEQ ZILOUT
8299 85 B2 STA LIVES+1
Change amount of lives at $8290 (EPROM $0290) from $A9$04 to $A9$0E (NTSC).
Change amount of lives at $82B6 (EPROM $02B6) from $A9$04 to $A9$0E (PAL).
NTSC GALAGA-14
Image may be NSFW.
Clik here to view.
GALAGA14_NTSC_B47B.bin 32K
14 downloads
Image may be NSFW.
Clik here to view.
Galaga14_NTSC_32K.a78 32.13K
17 downloads
PAL GALAGA-14
Image may be NSFW.
Clik here to view.
GALAGA14_PAL_781D.bin 48K
8 downloads
Image may be NSFW.
Clik here to view.
Galaga14_PAL_48K.a78 48.13K
9 downloads
ENJOY THE GAME!
NEXT UP> MS. PACMAN due out January 28th. Yes, another Monday. Two great sample games to be had with this release of the disassembly! Then vacation and then eventually the ROBOTRON disassembly re-hash, due to the popular conversion-to-PAL demand.
BAM!
BAM! BLUE AZURE MONDAY BAM!
BAM!
BAM!BAM!BAM!BAM!
GALAGA is next in the series of about 10 originals on the Atari 7800. It was a huge hit when it burst into arcades in 1981. It was a sequel to 1979's GALAXIAN, which also spawned several sequels of its own, is an intense space shooter. In 1984 this was to be the 7800's answer to the 5200's GALAXIAN.
DISASSEMBLY NOTES (true for all disassemblies)…
Thus far, not a single Atari 7800 .asm file has matched the corresponding released binary 100%. This isn't a surprise, nor a bad reflection of the engineers involved. We know there was a gap between the original designs of ca.1983-1984 and the eventual release of ca.1986. This was a period of unknown potential design changes at Atari, and the changes aren't documented as far as we know. The carts were released and they work, as they work. The original cart designs have been frozen for decades, never-ever reviewed in detail as they are now. To locate the differences between the released source list and the released binary, simply open the disassembly .rtf file and do a text search for "source" (without the quotes) and you'll see red text highlighting the differences. The green text is program comments and disassembly comments are in black. It's that simple. And whenever I see a typo error I clean those up as well. "Missle" should be spelled Missile, and now it is.
GALAGA Disassembly…
Image may be NSFW.
Clik here to view.
GalagaDisassembly6.rtf 475.83K
12 downloads(CAUTION: This is over 200 pages).
DEVELOPMENT OF GALAGA-14…
GALAGA was another fave of mine in the late 1980s. At first I was avoiding the macro-beams deployed by the Galagan Flagships, only to find out this is the way to get dual ships, but you have to follow the instructions (see the user's manual). Before developing my custom GALAGA game, I was thinking of naming my custom game GALAGAGA, but then I thought of Lady Gaga, which immediately changed my mind. To retain the look & feel of the original GALAGA game, I tended avoid creating invincibility for this game. Results of testing the changing of the start # of lives count with the ProSystem Emulator 1.3 (and confirmed on the 7800 hardware):
If the game starts with over 36 (24 hex) lives, the game crashes. If the game starts with over 20 (14 hex) lives, the game won't display the level number. The game will display up to 14 (0E hex) ships, so that's what we start with. This way, at the first death you will see a ship lost. Hence the name GALAGA-14. At first it may be disconcerning to see all these ships along the bottom, but this means more lives and more game time to achieve higher levels. Without more modification, no 99 lives or invincibility is immediately available. The game does offer some amazing opportunities for modifications I hope to build later, when more time is available.
HOW IT WAS DONE...
Looking at the disassembled code:
ATITOUT:
8290 A9 04 LDA #$04
8292 85 B1 STA LIVES
8294 AE 23 27 LDX TWOPLAYR
8297 F0 02 BEQ ZILOUT
8299 85 B2 STA LIVES+1
Change amount of lives at $8290 (EPROM $0290) from $A9$04 to $A9$0E (NTSC).
Change amount of lives at $82B6 (EPROM $02B6) from $A9$04 to $A9$0E (PAL).
NTSC GALAGA-14
Image may be NSFW.
Clik here to view.
GALAGA14_NTSC_B47B.bin 32K
14 downloadsImage may be NSFW.
Clik here to view.
Galaga14_NTSC_32K.a78 32.13K
17 downloadsPAL GALAGA-14
Image may be NSFW.
Clik here to view.
GALAGA14_PAL_781D.bin 48K
8 downloadsImage may be NSFW.
Clik here to view.
Galaga14_PAL_48K.a78 48.13K
9 downloadsENJOY THE GAME!
NEXT UP> MS. PACMAN due out January 28th. Yes, another Monday. Two great sample games to be had with this release of the disassembly! Then vacation and then eventually the ROBOTRON disassembly re-hash, due to the popular conversion-to-PAL demand.