GPU/External Registers

This page describes the address range used to configure the basic GPU functionality. Note that 3D rendering setup is not done via MMIO but instead by loading GPU command lists by writing to 0x1EF018F0.

Map

• 0x1EF00400 is the top screen
• 0x1EF00500 is the bottom screen

Init Values from nngxInitialize for Top Screen

• 0x1EF00400 = 0x1C2
• 0x1EF00404 = 0xD1
• 0x1EF00408 = 0x1C1
• 0x1EF0040C = 0x1C1
• 0x1EF00410 = 0
• 0x1EF00414 = 0xCF
• 0x1EF00418 = 0xD1
• 0x1EF0041C = 0x1C501C1
• 0x1EF00420 = 0x10000
• 0x1EF00424 = 0x19D
• 0x1EF00428 = 2
• 0x1EF0042C = 0x1C2
• 0x1EF00430 = 0x1C2
• 0x1EF00434 = 0x1C2
• 0x1EF00438 = 1
• 0x1EF0043C = 2
• 0x1EF00440 = 0x1960192
• 0x1EF00444 = 0
• 0x1EF00448 = 0
• 0x1EF0045C = 0x19000F0
• 0x1EF00460 = 0x1c100d1
• 0x1EF00464 = 0x1920002
• 0x1EF00470 = 0x80340
• 0x1EF0049C = 0

More Init Values from nngxInitialize for Top Screen

• 0x1EF00468 = 0x18300000, later changed by GSP module when updating state, framebuffer
• 0x1EF0046C = 0x18300000, later changed by GSP module when updating state, framebuffer
• 0x1EF00494 = 0x18300000
• 0x1EF00498 = 0x18300000
• 0x1EF00478 = 1, doesn't stay 1, read as 0
• 0x1EF00474 = 0x10501

0x1EF00010

Register address	Description
0x1EF000X0	Buffer physical address>>3
0x1EF000X4	Associated buffer physical address>>3
0x1EF000X8	Buffer size
0x1EF000XC	The low u16 for this register is overwritten by the GX command u16 parameter

These registers are used by GX command 2. 0x1EF00010 is used for the GX command buf0 parameters, while 0x1EF00020 is used for the GX command buf1 parameters.

0x1EF00X5C

Bit	Description
15-0	Framebuffer width
31-16	Framebuffer height

This controls the displayed LCD framebuffer dimensions.

0x1EF00X70

Bit	Description
15-0	Framebuffer format
31-16	?

Framebuffer format

Bit	Description
2-0	Color format
3	?
4	Unused?
5	Set when the main screen 3D right framebuffer address is set.
6	1 = main screen, 0 = sub screen. However if bit5 is set, this bit is cleared.
7	?
9-8	Value 1 = unknown: get rid of rainbow strip on top of screen, 3 = unknown: black screen.
15-10	Unused?

GSP module only allows the LCD stereoscopy to be enabled when bit5=1 and bit6=0 here. When GSP module updates this register, GSP module will automatically disable the stereoscopy if those bits are not set for enabling stereoscopy.

Framebuffer color formats

Value	Description	Actual color components ordering
0	GL_RGBA8_OES
1	GL_RGB8_OES	BGR
2	GL_RGB565_OES	RGB
3	GL_RGB5_A1_OES
4	GL_RGBA4_OES

0x1EF00X78

Bit	Description
0	LCD framebuffer to display (0=first, 1=second)
7-1	?
31-8	Unused

0x1EF00X90

Bit	Description
31-0	Framebuffer width * pixel byte-size.

Framebuffers

Process Virtual Address	Kernel Virtual Address	Physical Address	Description
0x1EF00468	0xFFFCE468	0x10400468	Main LCD, first framebuffer for 3D left
0x1EF0046C	0xFFFCE46C	0x1040046C	Main LCD, second framebuffer for 3D left
0x1EF00494	0xFFFCE494	0x10400494	Main LCD, first framebuffer for 3D right
0x1EF00498	0xFFFCE498	0x10400498	Main LCD, second framebuffer for 3D right
0x1EF00568	0xFFFCE568	0x10400568	Sub LCD, first framebuffer
0x1EF0056C	0xFFFCE56C	0x1040056C	Sub LCD, second framebuffer
0x1EF00594	0xFFFCE594	0x10400594	Sub LCD, unused first framebuffer
0x1EF00598	0xFFFCE598	0x10400598	Sub LCD, unused second framebuffer

The above framebuffer registers contains the physical address for each framebuffer, normally located in FCRAM in the application's GSP heap. When other processes use GSP as well, the framebuffers for the process is stored in VRAM instead.

These LCD framebuffers normally contain the last rendered frames from the GPU. The framebuffers are drawn from left-to-right, instead of top-to-bottom.(Thus the beginning of the framebuffer is drawn starting at the left side of the screen)

Both of the 3D screen left/right framebuffers are displayed regardless of the 3D slider's state, however when the 3D slider is set to "off" the 3D effect is disabled. Normally when the 3D slider's state is set to "off" the left/right framebuffer addresses are set to the same physical address. When the 3D effect is disabled and the left/right framebuffers are set to separate addresses, the LCD seems to alternate between displaying the left/right framebuffer each frame.

0x1EF00C00

Register address	Description
0x1EF00C00	Input GPU framebuffer physical address>>3
0x1EF00C04	Output LCD framebuffer physical address>>3
0x1EF00C08	Output framebuffer dimensions, used with cmd3
0x1EF00C0C	Input framebuffer dimensions, used with cmd3
0x1EF00C10	Flags, used with cmd3 and cmd4.
0x1EF00C14	GSP module writes value 0 here prior to writing to 0x1EF00C18, for cmd3.
0x1EF00C18	Writing value 1 here triggers GPU processing for the specified buffers.
0x1EF00C20	Unknown, used with cmd4
0x1EF00C24	Unknown, used with cmd4
0x1EF00C28	Unknown, used with cmd4

These registers are used by GX command 3 and 4. For cmd4, *0x1EF00C18 |= 1 is used instead of just writing value 1. The dimensions fields seem to use the same format as LCD register 0x1EF00X5C. The input framebuffer width for the main screen is normally 480.

0x1EF00C10

Bit	Description
0	When set, the framebuffer data is flipped vertically.(Normally zero)
1	Unknown, normally zero.
2	This bit is set when the out-framebuf width/height is less than the input framebuf width/height, clear otherwise. Bit24 is normally clear when this bit is set.
4-3	Unused
5	Unknown, normally zero.
7-6	Unused
10-8	Input framebuffer color format, value0 and value1 are the same as the LCD framebuffer formats.(Usually zero)
11	Unused
14-12	Output framebuffer color format
15	Unused
16	When this is set, the framebuffer data is converted to tiles.(Normally zero)
19-17	Unused
21-20	Unknown, output framebuffer data doesn't seem to change when this value is changed.(Normally zero)
23-22	Unused
24	This is set when the input_framebufwidth = output_framebufwidth<<1.
31-25	Unused

0x1EF018E0

Register address	Description
0x1EF018E0	Buffer Size>>3
0x1EF018E8	Buffer physical address>>3
0x1EF018F0	Writing value 1 here triggers GPU processing for the specified buffer

These 3 registers are used by GX command 1. This is used for GPU commands.