ATARI 7800 BANKSWITCHING GUIDE
From 8BitDev.org - Atari 7800 Development Wiki
ATARI 7800 BANKSWITCHING GUIDE
(c) copyright by Eckhard Stolberg (Eckhard_Stolberg@web.de)
last modified on April 8, 2008 (version 1.40)
Thanks to:
Lee Krueger, Graham Percy, Dan Boris, Chad Schell and Mitch Orman
==============================================================================
7800 games can use the memory from $0400 to $047f, from $0500
to $17ff and from $2800 to $ffff, but only the High-Score cart
uses anything below $4000. It has 4KB of ROM at $3000-$3fff
and 2KB of battery-backed RAM at $1000-$17ff.
The non bankswitching games (7808, 7816, 7832 and 7848) just
use the specified amount of ROM from $ffff downwards.
Then there are several different types of Atari's SuperGame
bankswitching. It basically consists of 8 16KB banks (0-7)
that can be mapped in at $8000-$bfff. Bank 7 always is fixed
at $c000-$ffff. To map in a chosen bank into $8000-$bfff you
write it's bank number (0-7) to any address between $8000-bfff.
The contend of $4000-$7fff differs between different variations
of this type:
Some games have nothing connected in this area and return only
random data.
Some games have bank 6 fixed at this area.
Some games have 16K of extra ROM there. Those games are 144K
in size and are marked as 78S9 in the list.
Some games have either 8K of RAM at $6000-$7fff or 16K of
RAM at $4000-$7fff.
Some games have a POKEY chip mapped in at this area. It
has 16 addresses that get repeated all the way between $4000
and $7fff.
Some games only have 4 ROM banks at $8000-$bfff (0-3). Banks
4-7 either return the same data as banks 0-3 or completely
random data. PAL Karateka is a special case. It only uses
banks 4-7. Banks 0-3 are random data and bank 6 is also fixed
at $4000-$7fff.
F18 Hornet has it's own bankswitching format (78AB). It has
32K of fixed data at $8000-$ffff and 2 16K banks at $4000 -
$7fff. The two banks get mapped in by writing either $01 or
$02 to address $8000. I don't know if other addresses trigger
the bankswitching too, but I'm assuming any address above
$8000 might work. I have no idea what happens when you write
other values to the hotspot, but they probably will just be
ignored.
Double Dragon and Rampage have a very wierd bankswitching
scheme (78AC). It has 8 16K banks (0-7) that get mapped in at
$a000-$dfff. Write accesses to addresses above $ff80 trigger
the bankswitching. This sets the bank according to the low
nibble of the address. So a write to $ff80 maps in bank 0,
a write to $ff81 maps in bank 1, etc. The games only use
addresses $ff80-$ff87, so I'm not sure if other addresses
trigger the bankswitching too.
If we are assuming that a bank reaches from $a000-$dfff,
then the rest of the ROM space looks like this:
$4000-$5fff second 8kb of bank 6
$6000-$7fff first 8kb of bank 6
$8000-$9fff second 8kb of bank 7
$e000-$ffff first 8kb of bank 7
The Rescue on Fractalus prototype only has 32K of ROM.
But it also has 2K of RAM with a unique mapping. The RAM
is devided into 8 blocks of 256 bytes. Each block is repeated
twice in the memory area between $4000-$4fff. So block 1
would appear at $4000-$40ff and at $4100-$41ff, block 2
would be at $4200-$42ff and at $4300-$43ff, etc. This setup
allows the game to create double-scanline graphics for the
landscape display in a fast and space efficient way.
Type RAM POKEY TV Name
78SG 0 no NTSC Ace of Aces
78S9 0 no NTSC Alien Brigade
7816 0 no NTSC Asteroids
7832 0 yes NTSC Ballblazer
78SG 0 no NTSC Barnyard Blaster
78SG 0 no NTSC Basketbrawl
7816 0 no NTSC Centipede
7832 0 no NTSC Choplifter!
78S9 0 no NTSC Chuck Norris: Missing in Action (prototype)
78SG 0 yes NTSC Commando
7808 0 no NTSC Colour Test
78SG 0 no NTSC Crack'ed
78S9 0 no NTSC Crossbow
78SG 0 no NTSC Dark Chambers
7848 0 no NTSC Desert Falcon
7816SG 144 no NTSC Development Cartridge (Atari)
7816 0 no NTSC Diagnostic Cartridge
7816 0 no NTSC Dig Dug
7848 0 no NTSC Donkey Kong
7848 0 no NTSC Donkey Kong Junior
78AC 0 no NTSC Double Dragon
78AB 0 no NTSC F18 Hornet
78SG 0 no NTSC Fatal Run
78SG 0 no NTSC Fight Night
7832 0 no NTSC Food Fight
7832 0 no NTSC Galaga
7848 0 no NTSC GATO (prototype)
7848 0 no NTSC Hatrick
78HS 2 no NTSC High-Score Cartridge (RAM is battery backed)
78SG 0 no NTSC Ikari Warriors
78SG 8 no NTSC Impossible Mission
78SG 8 no NTSC Jinks
7832 0 no NTSC Joust
7848 0 no NTSC Karateka
78SG 0 no NTSC KLAX (prototype)
7832 0 no NTSC Kung-Fu Master
7848 0 no NTSC Mario Bros.
78SG 0 no NTSC Mat Mania Challenge
78SG 0 no NTSC Mean 18 Ultimate Golf
78SG 0 no NTSC Meltdown
78SG 0 no NTSC Midnight Mutants
7804 0 no NTSC Monitor Cartridge (Harry Dodgson)
(early versions had only a 4K 7800 mode)
7816*2 8 no NTSC Monitor Cartridge (Harry Dodgson)
(16KB for 7800 mode and 16KB for 2600 mode
RAM is battery backed)
78SG 0 no NTSC Motor Psycho
7816 0 no NTSC Ms. Pac-Man
78SG 0 no NTSC Ninja Golf
7848 0 no NTSC One on One Basketball
7832 0 no NTSC Pete Rose Baseball
78S4 0 no NTSC Pitfighter (prototype)
78SG 0 no NTSC Planet Smashers
78SG 16 no NTSC Plutos (prototype)
7832 0 no NTSC Pole Position II
78AC 0 no NTSC Rampage
78SG 0 no NTSC Rampart (prototype)
78S4 0 no NTSC Realsports Baseball
7832+ 2 no NTSC Rescue on Fractalus (prototype)
7832 0 no NTSC Robotron
78SG 0 no NTSC Scrapyard Dog
78SG 0 no NTSC Sentinel (prototype)
78SG 16 no NTSC Sirius (prototype)
78SG 16 no NTSC Summer Games
7848 0 no NTSC Super Huey UH-IX
7832 0 no NTSC Super Skateboardin'
78S4 0 no NTSC Tank Command
7832 0 no NTSC Titlematch Pro Wrestling
7832 0 no NTSC Tomcat F14
78SG 0 no NTSC Touchdown Football
78S4 8 no NTSC Tower Toppler
78S4 0 no NTSC Waterski
78SG 16 no NTSC Winter Games
78SG 0 no NTSC Xenophobe
7832 0 no NTSC Xevious
7800 Computer Keyboard modules:
7816 0 no NTSC AtariLab Light Module
7816 0 no NTSC AtariLab Temperature Module
7840 8 no NTSC AtariTerm (?)
(RAM at $4000-$5fff)
7816 16 no NTSC OSS / Atari 7800 BASIC
(RAM might be at $8000-$bfff)
7832 16 no NTSC VideoWriter
missing:
Sky Fox (?)
78SG 0 no PAL Ace of Aces
78S9 0 no PAL Alien Brigade
7816* 0 no PAL/NTSC Asteroids (BIOS)
7832 0 yes PAL Ballblazer
78SG 0 no PAL Barnyard Blaster
78SG 0 no PAL Basketbrawl
7816 0 no PAL Centipede
7848 0 no PAL Choplifter!
78SG 0 yes PAL Commando
78SG 0 no PAL Crack'ed
78S9 0 no PAL Crossbow
78SG 0 no PAL Dark Chambers
7848 0 no PAL Desert Falcon
7832 0 no PAL Dig Dug
7848 0 no PAL Donkey Kong
7848 0 no PAL Donkey Kong Junior
78AC 0 no PAL Double Dragon
78AB 0 no PAL F18 Hornet
78SG 0 no PAL Fatal Run
78SG 0 no PAL Fight Night
7848 0 no PAL Food Fight
7848 0 no PAL Galaga
7848 0 no PAL Hat Trick
78SG 0 no PAL Ikari Warriors
78SG 8 no PAL Impossible Mission
78SG 8 no PAL Jinks
7848 0 no PAL Joust
78S4 0 no PAL Karateka (uses banks 4-7 instead of 0-3)
7832 0 no PAL Kung-Fu Master
7848 0 no PAL Mario Bros.
78SG 0 no PAL Mat Mania Challenge
78SG 0 no PAL Mean 18 Ultimate Golf
78SG 0 no PAL Meltdown
78SG 0 no PAL Midnight Mutants
78SG 0 no PAL Motor Psycho
7832 0 no PAL Ms. Pac-Man
78SG 0 no PAL Ninja Golf
7848 0 no PAL One on One Basketball
7832 0 no PAL (Pete Rose) Baseball
78SG 0 no PAL Planet Smashers
7832 0 no PAL Pole Position II
78SG 0 no PAL Scrapyard Dog
78SG 0 no PAL Sentinel
7848 0 no PAL Super Huey UH-IX
7832 0 no PAL Super Skateboardin'
7832 0 no PAL Titlematch Pro Wrestling
7832 0 no PAL Tomcat F14
78S4 8 no PAL Tower Toppler
78SG 0 no PAL Xenophobe
7848 0 no PAL Xevious
no PAL version released (?):
Rampage
Realsports Baseball
Robotron
Summer Games
Tank Command
Touchdown Football
Water Ski
Winter Games
