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
| User VA | PA | Length | Name | Comments |
|---|---|---|---|---|
| 0x1EF00004 | 0x10400004 | 4 | ? | |
| 0x1EF00010 | 0x10400010 | 16 | MemoryFill1 (GX command 2) | |
| 0x1EF00020 | 0x10400020 | 16 | MemoryFill2 (GX command 2) | |
| 0x1EF00030 | 0x10400030 | 4 | ||
| 0x1EF00400 | 0x10400400 | 0x100 | Top Screen Framebuffers | |
| 0x1EF00500 | 0x10400500 | 0x100 | Bottom Screen Framebuffers |
MemoryFill 0x1EF00010/0x1EF00020
| User VA | 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.
Screen 0x1EF00400/0x1EF00500
| Offset | Length | Name | Comments |
|---|---|---|---|
| 0x5C | 4 | Framebuffer width & height | Lower 16 bits: width, upper 16 bits: height |
| 0x68 | 4 | Framebuffer A first address | For top screen, this is the left eye 3D framebuffer. |
| 0x6C | 4 | Framebuffer A second address | For top screen, this is the left eye 3D framebuffer. |
| 0x70 | 4 | Framebuffer format | Bit0-15: framebuffer format, bit16-31: unknown |
| 0x78 | 4 | Framebuffer select | Bit0: which framebuffer to display, bit1-7: unknown |
| 0x90 | 4 | Framebuffer size | Framebuffer width * pixel byte-size. |
| 0x94 | 4 | Framebuffer B first address | For top screen, this is the right eye 3D framebuffer. Unused for bottom screen. |
| 0x98 | 4 | Framebuffer B second address | For top screen, this is the right eye 3D framebuffer. Unused for bottom screen. |
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 |
Framebuffers
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 | When set, the framebuffer data is converted to tiles. (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. |
| 3 | When set, the framebuffer data is copied linearly, without doing any conversion (by default it is converted from tiles to linear). This has priority over bit1. |
| 4 | 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.
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