GPU/Commands

This page describes the structure of the buffer for GX command 1 with the registers at 0x1EF018E0. This buffer is used for GPU commands including OpenGL commands, each 8-byte entry in the buffer is a command. Cmd+0 is the command parameter, and cmd+4 is the command header.

Invalid GPU command parameters can cause the GPU to hang, this then causes the GSP module to hang as well.

Command Header

Bit	Description
19-0	Command ID
30-20	Total words following the command, if any.
31	?

The first word in the parameter data structure is the command parameter value, the rest of the data structure is from the data following the command. The word after the last data structure word is padding when needed for 8-byte alignment, for the following command.

Commands

CommandID	Parameter	Description
0x000F0010	Value is 0x12345678	This command is always the last command in the buffer.
0x000F0110	Value 0x1	This command is immediately before CmdID 0x000F0010, this is also used elsewhere for beginning rendering of object(s) as well.
0x000F0111	Value 0x1	This command is immediately before CmdID 0x000F0110, however CmdID 0x000F0110 doesn't always follow this command.
0x000F0040	u32, valid values are 0x1 and 0x2, values 0x0 and 0x3 have the same effect as value 0x2. Only bits 1-0 are used.	Disable/enable alpha testing. Parameter value 0x1 disables GL_ALPHA_TEST, while value 0x2 enables GL_ALPHA_TEST.
0x000F0041	float	This is used to initialize the projection matrix?
0x000F0042	float	This is used immediately after CmdID 0x000F0043, for the third parameter for CmdID 0x000F0041.
0x000F0043	float	This is used immediately after CmdID 0x000F0041, for the second parameter.
0x000F0044	float	This is used immediately after CmdID 0x000F0042, for the fourth parameter for CmdID 0x000F0041.
0x801F004D	First word in parameter structure	?
0x0002025E	u32, val<<8. Val3 = GL_TRIANGLES, val5 = GL_TRIANGLE_STRIP, val6 = GL_TRIANGLE_FAN. Val0 and val4 are unknown, these seem to have the same effect.	This sets the GL rendering mode.
0x000F0068	u32	This is used immediately after CmdID 0x000F0044.
0x000F006E	u32	This is used immediately after CmdID 0x000F011E, with the same input parameter value as CmdID 0x000F011E.
0x809F0081		This is used to set the current texture info used for rendering.
0x000F008E	u32	This texture-related command is used immediately after CmdID 0x809F0081.
0x00020100	u32, value is 0x00E40100	This command is used immediately before CmdID 0x000F0101.
0x000F0101	u32	Color related?
0x000F0116	u32	Unknown, this is used immediately after CmdID 0x000F011D.
0x000F0117	u32	Unknown, normally the input parameter is value 0x2.
0x000F011C	Physical address>>3	Normally this address is located in VRAM, this seems to be the GPU data storage end address. This command is used immediately after 0x000F0116.
0x000F011D	Physical address>>3	This initializes the framebuffer address used for rendering, this framebuffer is used for the input framebuffer with GX command 3 and 4. This is also the GPU data storage start address, this data storage likely contains vertex arrays, etc. This command is used immediately after CmdID 0x000F0117.
0x000F011E	u32	This sets the width and height for the framebuffer used for rendering. Therefore this is glViewport() with x=0 and y=0. This is used immediately after CmdID 0x000F011C.
0x8XXF0200		The first word in the parameter buffer structure seems to have a similar same effect as CmdID 0x000F0040, where param0 = val<<24.(Val 0x3 enables alpha testing, while other values disables it)
0x000F0227	u32, bit31 is unknown. Bits30-0 is the address, where address is relative to VRAM.	This specifies the address of an array containing vertex array indices, used for rendering primitives. Each index entry is an u16.
0x000F0228	u32 total elements in the array to use for rendering.	This command is used immediately after CmdID 0x000F0227. This command and CmdID 0x000F0227 are some of the commands used for glDrawElements().
0x000F02B0	u32, value is 0x7FFF0000 | val.	Texture related?
0x000F02C0	0x80000000 | Type	This is used immediately before CmdID 0xXXXF02C1. This type field controls the command parameter buffer type.
0xXXXF02C1	First word in the first entry	A list of entries follow this command.

Parameter value format for CmdID 0x000F011E

Bit	Description
11-0	Framebuffer width
23-12	Framebuffer height - 1
24	Must be set
31-25	Unused?

Normally the width and height is set to the same dimensions used with GX command 3 and 4.

Texture info parameter structure for CmdID 0x809F0081

Index Word	Description
0	?
1	The low u16 is the texture image width, and the high u16 is the texture image height.
2-3	?
4	Texture data physical address >> 3. This is normally located in the VRAM GPU data storage region.
5-9	?

Entries for CmdID 0xXXXF02C1

Index Word	Description
0	float
1	float
2	float

Color Entry

Index Word	Description
0	float Red component
1	float Blue component
2	float Green component
3	float Alpha?
4	float
5	float

Vertex Entry

Index Word	Description
0	float X coordinate
1	float Y coordinate
2	float Z coordinate

Type 0x14 seems to used for rendering quads, mainly for the skybox/sub screen etc. The rest of the rendered objects are likely rendered via vertex arrays, however it's unknown how the vertex arrays are initialized.

Types for CmdID 0x000F02C0

Value	Entries per chunk	Description
0x00	4	Related to model-view matrix translation?
0x04	4	Unknown, this is used immediately after type 0x00.
0x08	One color entry via two CmdID 0xXXXF02C1 entries.	Sets the color.
0x0A	4	Texture coordinates related?
0x0B	3	?
0x0C, 0x0D	3	Related to type 0x0A?
0x0E	4	Related to type 0x0A?
0x14	<=30	Geometry vertices
0x4C	4	?
0x50, 0x53, and 0x56	1	?
0x51, 0x54, and 0x57	1	?
0x52, 0x55, and 0x58	1	?
0x59	1	Unknown, the entry data is floats converted from s32s.
0x5A	2	Color related?
0x5C	1	?