Yet Another Gamecube Documentation

4 Memory Map

4.1 Overview

start	end	size	description
`0x00000000`	`0x017fffff`	24MB	Physical address of the RAM
`0x80000000`	`0x817fffff`	24MB	Logical address of the RAM, cached
`0xC0000000`	`0xC17fffff`	24MB	Logical address of the RAM, not cached
`0xc8000000`		2MB	Embedded Framebuffer (EFB)
`0xCC000000`			Hardware registers
`0xCC000000`			CP - Command Processor
`0xCC001000`			PE - Pixel Engine
`0xCC002000`			VI - Video Interface
`0xCC003000`			PI - Processor Interface (Interrupt Interface)
`0xCC004000`			MI - Memory Interface
`0xCC005000`			AI - Audio Interface
`0xCC006000`			DI - DVD Interface
`0xCC006400`			SI - Serial Interface
`0xCC006800`			EXI - External Interface
`0xCC006C00`			Streaming Interface
`0xCC008000`			GX FIFO (Graphic display lists)
`0xe0000000`	`0xe0003fff`	16k	L2 Cache
`0xfff00000`		1MB	IPL (mapped here at bootup)

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4.2 RAM usage

Variables that are marked as B are changed by bootrom or IPL. Variables marked as A are changed lately in apploader when a game is booting. Variables, which are marked as O are changed after an OSInit call. Remember that the IPL also has a hard-linked Dolphin OS inside, so those variables that are marked as O are also changed in the IPL.

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4.2.1 Dolphin-OS globals

In PowerPC architectures the lower 256 bytes of main memory are reserved for internal OS use. This map describes all known OS low memory variables. Dolphin OS accesses low memory as 0x80000000 + offset (cached).

4.2.1.1 Boot Info

4.2.1.1.1 DVD Disc ID

start size description

0x80000000 0x04 B Gamecode

0x80000004 0x02 B Company

0x80000006 0x01 B Disk ID

0x80000007 0x01 B Version

0x80000008 0x01 B Streaming

0	audio streaming off
1	audio streaming on

0x80000009 0x01 B StreamBufSize

0x8000000a 0x0f padding zeros

4.2.1.1.2 system Info

start size description

0x8000001c A DVD magic word

0xc2339f3d Nintendo Game Disc

0x80000020 4 A Magic word (how did the console boot?)

value	description
`0x0D15EA5E`	normal boot
`0xE5207C22`	booted from jtag

0x80000024 4 A Version (usually set to 1 by apploader)

0x80000028 4 B physical Memory Size

0x01800000 24MB on retail console

0x8000002C 4 B Console type

value	Description
`0x00000001`	Retail1
`0x00000002`	HW2 production board
`0x00000003`	The latest production board
`0x00000004`	Reserved
`0x1XXXXXXX`	Devkits
`0x10000000`	MAC emulator
`0x10000001`	PC Emulator
`0x10000002`	'Arthur'
`0x10000003`	'Minnow'
`0x10000004`	1st Devkit HW
`0x10000005`	2nd Devkit HW
`0x10000006`	latest Devkit HW
`0x10000007`	Reserved
`0x2XXXXXXX`	TDEV-kits
`0x20000005`	HW2 TDEV system
`0x20000006`	The latest TDEV system
`0x20000007`	Reserved

0x80000030 4 O ArenaLo (==0x00000000)

0x80000034 4 O ArenaHi (==0x817fe8c0)

0x80000038 4 FST Location in ram (==0x817fe8c0)

0x8000003C 4 FST Max Length (==0x00000024)

4.2.1.2 Debugger info

start	size		description
`0x80000040`	`4`	A	flag for "debugger present" (used by __OSIsDebuggerPresent)
`0x80000044`	`4`	A	Debugger Exception mask Bitmap, set to 0 at sdk lib start
`0x80000048`	`4`	A	Exception hook destination (physical address)
`0x8000004c`	`4`	A	Temp for LR, Return from exception address (to return from hook)
`0x80000050`	`16`		padding zeros

4.2.1.3 Debugger Hook

.>80000060 38 a0 00 40 li r5,0x40

r5=0x40

.>80000064 7c 68 02 a6 mflr r3

r3=lr

.>80000068 90 65 00 0c stw r3,0x0c(r5)
.>8000006c 80 65 00 08 lwz r3,0x08(r5)
.>80000070 64 63 80 00 oris r3,r3,0x8000
.>80000074 7c 68 03 a6 mtlr r3

lr=r3

.>80000078 38 60 00 30 li r3,0x30
.>8000007c 7c 60 01 24 mtmsr r3

msr=0x30

.>80000080 4e 80 00 20 blr

jump (lr)

4.2.1.4 Dolphin OS Globals

start end size description

0x80000084 0x800000bf padding zeros

0x800000c0 4 O Current OS context (physical address)

0x800000C4 4 O Previous OS interrupt mask

0x800000C8 4 O current OS interrupt mask

0x800000CC TV Mode

value	description
0	ntsc
1	pal
2	debug
3	debug pal
4	mpal
5	pal 60

0x800000d0 B ARAM size (internal+expansion) in bytes. set by ARAM driver, usually 16mb.

0x800000D4 O current OS Context (logical address)

0x800000D8 O default OS thread (logical address)

0x800000Dc O active Thread queue, head thread (logical address)

0x800000e0 O active Thread queue, tail thread (logical address)

0x800000e4 O Current OS thread

0x800000e8 A Debug monitor size (in bytes)

0x800000ec A Debug monitor location (usually at the top of main memory)

0x800000F0 A Console Simulated Memory Size, 0x01800000 (usually same as physical memory size)

0x800000F4 A DVD BI2 location in main memory (size of BI2 is 0x2000 bytes)

0x800000F8 Bus Clock Speed, 162 MHz (=0x09a7ec80, 162000000)

0x800000FC CPU Clock Speed, 486 MHz (=0x1cf7c580, 486000000)

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4.2.2 Exception Handlers

start	end	size	description
`0x80000100`			System Reset Interrupt
`0x80000200`			Machine Check Interrupt
`0x80000300`			DSI Interrupt
`0x80000400`			ISI Interrupt
`0x80000500`			External Interrupt
`0x80000600`			Alignment Interrupt
`0x80000700`			Program Interrupt
`0x80000800`			FP unavailable Interrupt
`0x80000900`			Decrementer Interrupt
`0x80000C00`			System Call Interrupt
`0x80000d00`			Trace Interrupt
`0x80000f00`			Performance Monitor Interrupt
`0x80001300`			IABR Interrupt
`0x80001400`			reserved
`0x80001700`			Thermal Interrupt
`0x80001800`	`0x80002fff`		unused/reserved (*)

(*) note: psoload v2 uses this area to stay resident in memory, it is unused by Dolphin-OS

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4.2.3 Dolphin-OS globals

start end size Description

0x80003000 exception handler vectors (from sdk libs & ipl)

0x8000303c 4 padding/unused

0x80003040 external interrupt handler vectors (from sdk libs & ipl)

0x800030a4 padding/unused

0x800030c0 4 ?

0x800030c4 4 ?

0x800030c8 4 First Module Header Pointer in Module Queue

0x800030cc 4 Last Module Header Pointer in Module Queue

0x800030d0 4 Module String Table Pointer

0x800030d4 4 A DOL size (total size of text/data sections), in bytes (*1)

0x800030d8 4 B OS system time (set, when console is powered up)

0x800030dc 4 ?

0x800030E0 4 ? (6=production pads ?)

0x800030e4 2 ?

0x800030e6 1 ?

0x800030e7 1 ?

0x800030e8 1 O set by OsInit() (debugger stuff?)

0x800030e9 1 O set by OsInit() (debugger stuff?)

0x800030ea 2 ?

0x800030ec 4 ?

0x800030F0 2 ?

0x800030F2 1 Boot status

value	description
0	first boot
1	already booted

0x800030F3 1 ?

0x800030F4 4 ?

0x800030F8 4 ?

0x800030Fc 4 ?

(*1) If FST on DVD is placed after DOL, then BB2 FSTLength is added to this value.

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4.2.4 User Memory

4.2.4.1 user program area

start	end	size	description
`0x80003100`			Start of code (usually)
`0x80003140`			Entry point (early SDK v1.0 applications)
`0x81200000`			Load Address of the Apploader
`0x81300000`			Load Address of Bootrom/IPL

note: of course the entrypoint of an application can be anything, those listed here are just some typical examples. Retail game start dol-files are usually located below the apploader.

4.2.4.2 stack area

start	end	size	description
			Bottom of Stack
			Top of Stack

4.2.4.3 heap area

start	end	size		description
`?`			O	ArenaLo - Bottom of Heap
`0x817fe8c0`			O	ArenaHi - Top of Heap

note: the address of ArenaHi is not a constant, but should be set to the bottom of the FST which is read from the DVD so its size depends on the application. the value given here is just an example. 4.2.4.4 'high memory'

start	end	size		description
`0x817fe8c0`		`24`	O	FST (used by Dolphin-OS)
`0x817fffff`				Memory Top

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