From SMS Power!

Development: Memory Map


This page gives a fast reference to the memory maps of Sega 8-bit consoles. See other pages for more detailed information.

Master System/Mark III/Game Gear

RegionMaps to
$0000-$bfffCartridge (ROM/RAM/etc) (or other attached hardware)
$c000-$dfffSystem RAM
$e000-$ffffSystem RAM (mirror)

The "Cartridge" region is defined by the currently active cartridge, card or expansion device (where applicable). In nearly all cases, these correspond to ROM or on-cartridge RAM.

Master System/Mark III (assuming Sega mapper)

RegionMaps to
$0000-$03ffROM (unpaged)
$0400-$3fffROM mapper slot 0
$4000-$7fffROM mapper slot 1
$8000-$bfffROM/RAM mapper slot 2
$c000-$dfffSystem RAM
$e000-$ffffSystem RAM (mirror)
$fff83D glasses control
$fff9-$fffb3D glasses control (mirrors)
$fffcCartridge RAM mapper control
$fffdMapper slot 0 control
$fffeMapper slot 1 control
$ffffMapper slot 2 control

Where control registers overlap with mirrored RAM, values written will affect the device and also be written to RAM. Reads simply return the value stored in RAM.


RegionMaps to
$0000-$bfffCartridge (ROM/RAM/etc)
$c000-$c3ffSystem RAM
$c400-$ffffSystem RAM (mirrored every 1KB)

Cartridges may disable the system RAM and thus take over the full 64KB address space.

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Page last modified on Thu Jan 19, 2017 12:42 am