| EAX | Scratch register |
| EBX | Z-buffer pixel address |
| ECX | Loop counter |
| EDX | Texture 0 pointer |
| ESI | Span-list pointer |
| EDI | Pixel-buffer pixel address |
| EBP | Texture 1 pointer |
| ESP | 1/z |
| MM0 | Texture 0 coordinates (u0, v0) |
| MM1 | Texture 1 coordinates (u1, v1) |
| MM2 | Gouraud color |
| MM3 | Specular color |
| MM4-MM7 | Scratch registers |