Systems Memory Mapping

Work in Progress

This page details how the memory of each supported system is mapped.

Memory banks as registered in the RA emulators are defined here.

NES

Reference: https://wiki.nesdev.com/w/index.php/CPU_memory_map

Bank	Offset	Length	Description
0	0x0000	0x0800	2KB internal RAM
1	0x0800	0x0800	Mirror of $0000-$07FF
2	0x1000	0x0800	Mirror of $0000-$07FF
3	0x1800	0x0800	Mirror of $0000-$07FF
4	0x2000	0x0008	PPU registers
5	0x2008	0x1FF8	Mirrors of $2000-$2008
6	0x4000	0x0018	APU and I/O registers
7	0x4018	0x0008	APU and I/O test registers
8	0x4020	0x1FE0	Cartridge data
9	0x6000	0x2000	Cartridge RAM
10	0x8000	0x8000	Cartridge ROM

SNES

https://en.wikibooks.org/wiki/Super_NES_Programming/SNES_memory_map

N64

https://raw.githubusercontent.com/mikeryan/n64dev/master/docs/n64ops/n64ops%23h.txt

GB

Reference: http://gameboy.mongenel.com/dmg

The memory map reflects the CPU memory space.

GBC

The memory map is identical to the Game Boy's, with the exception of banked work RAM. The first bank is mapped to its usual location in CPU space, while banks 2-7 are appended to the end of the memory map, in the 0x10000-0x15FFF region.

GBA

https://www.coranac.com/tonc/text/hardware.htm#sec-memory

VirtualBoy

Master System

Reference: http://www.codeslinger.co.uk/pages/projects/mastersystem/memory.html

TODO: find a more reliable source.

Offset	Length	Description
0x0C000	0x02000	RAM

MegaDrive (Genesis)

https://en.wikibooks.org/wiki/Genesis_Programming
https://wiki.megadrive.org/index.php?title=Main_68k_memory_map
see also Jamiras comment here: https://github.com/RetroAchievements/RALibretro/issues/47#issuecomment-455374796

GameGear

Atari 2600

Reference: http://www.randomterrain.com/atari-2600-memories-tutorial-andrew-davie-05.html#summary

Offset	Length	Description
0x080	0x080	RAM

Atari 7800

Atari Lynx

ColecoVision

NeoGeo Pocket

PCEngine (TurboGrafx16)

PCEngine CD

Arcade

PC-8001 / PC-8801

Reference: http://www.maroon.dti.ne.jp/youkan/pc88/memmap.html

The memory map is based on the PC-8801 layout, but excludes graphics VRAM and extended RAM.

PC-8801

Bank	Offset	Length	Description
0	0x00000	0x10000	Main RAM
1	0x10000	0x1000	Text VRAM

Text VRAM is also known as high-speed RAM, and is used as a main RAM area in some titles.

PC-8001

Reference: http://www.cyross.com/pc8801wiki

The entire memory space is mapped in the PC-8801 main RAM bank, but only RAM is exposed, so most of the mapped space will remain uninitialized.

Offset	Length	Description
0x08000	0x08000	RAM

Apple II

Reference: http://apple2.guidero.us/doku.php/mg_notes/general/mem_map

The memory map consists of both main and auxiliary RAM banks. Rather than mapping the CPU-accessible memory space, which can flicker at high frequencies, the RAM banks are mapped consecutively.

Auxiliary RAM is only available on systems with 128KB of RAM (Apple IIe and up), so it will remain uninitialized on 64KB systems or when running titles that are not designed to make use of auxiliary RAM.

Bank	Offset	Length	Description
0	0x00000	0x10000	Main RAM
1	0x10000	0x10000	Auxiliary RAM