The wiki has recently moved; please report any issues in Discord. Pardon the dust.
Xbox 360/Hardware information/Xenos (GPU)
A repository for ROMhacking relevant info for Xenos.
Basic Specifications
- ATI Xenos @ 500MHz
- World's first unified shading GPU
- TeraScale uarch
- 3 "SIMD cores" (predecessor to CUs)
- 8 ROPS
- 16 TMUs
- 240 shaders
- Direct3D Feature Level 9_0c, with some things from higher feature levels (mainly FL 10)
- MEMEXPORT allows for GPGPU compute
- Connected to 10MB of eDRAM framebuffer
- eDRAM has extremely high bandwidth and PIM for free MSAA at 720p and low-cost at 1080p
Things to note: If using data from MEMEXPORT on CPU, you must enable both d3d12_readback_memexport and d3d12_readback_resolve in Xenia's options or use HW!
ucode Programming
Xenos, like other Xbox consoles, is able to directly ingest and execute ucode without having to be compiled by the driver first, allowing programmers to squeeze out more performance by relying on the fixed HW spec.
| Instruction | Hex | Description |
|---|---|---|
| exec | 0x10 0x2A 0x11 0x** | Start executing code |
| (Unknown) | 0xFF 0xFF 0x03 0x** | NOP, end of program |
Texture Formats
| Format | Description | Xenos Specific | Other |
|---|---|---|---|
| Uncompressed | Bitmap | No | Not recommended due to high VRAM use |
| DXT1/BC1 | No | ||
| DXT2/BC2 | No | ||
| DXT3/BC2 | No | ||
| DXT3A | Yes | ||
| DXT3A as 1111 | Yes | ||
| DXT4/BC3 | No | ||
| DXT5/BC3 | No | ||
| DXT5A | Yes | ||
| DXN | Yes | ||
| CTX1 | Yes |
Useful Links
https://www.techpowerup.com/gpu-specs/xbox-360-gpu-90nm.c1919
https://learn.microsoft.com/en-us/windows/win32/direct3d9/dx9-graphics-reference
https://learn.microsoft.com/en-us/windows/win32/direct3d9/dx9-graphics-programming-guide
https://learn.microsoft.com/en-us/windows/win32/direct3d10/d3d10-graphics-reference
https://learn.microsoft.com/en-us/windows/win32/direct3d10/d3d10-graphics-programming-guide
https://en.wikipedia.org/wiki/Unified_shader_model
https://fileadmin.cs.lth.se/cs/Personal/Michael_Doggett/talks/unc-xenos-doggett.pdf
http://www.students.science.uu.nl/~3220516/advancedgraphics/papers/inferred_lighting.pdf