Sony PlayStationPortable, Документация

Страница: 113 / 157

11 3D GRAPHICS PROCESSING 113
11.5.194 TRXSPOS
0xeb
4 w TRXSPOS - Transfer Source Position
31 24 23 16 15 8 7 0
.... .... .... .... .... .... .... ....
bit(s) description
10-19 Y Position
0-9 X Position
11.5.195 TRXDPOS
0xec
4 w TRXDPOS - Transfer Destination Position
31 24 23 16 15 8 7 0
.... .... .... .... .... .... .... ....
bit(s) description
10-19 Y Position
0-9 X Position
11.5.196 TRXSIZE
0xee 4 w TRXSIZE - Transfer Size
31 24 23 16 15 8 7 0
.... .... .... .... .... .... .... ....
bit(s) description
10-19 Height = Transfer Height-1
0-9 Width = Transfer Width-1
11.6 Texture Cache
The texture cache is very important on the PSP (as it was on the PS2). From experiments it seems to be 8kB, so that means it’s 64x32
in 32-bit, 64x64 in 16-bit, 128x64 in 8-bit and 128x128 in 4-bit (the sizes are qualified guesses by looking at the PS2). Ordering your
draws so that locality in uv-coordinates is maximized will make sure your rendering is optimal.
DXTn is decompressed into 32-bit when loaded into the cache, so what you gain in shrinking the texture-size, you lose in texture-cache.
If you can, use 4- or 8-bit textures, which will allow a much larger area to be kept in the cache.
11.7 Memory Bandwidth
texture reads from user memory (mem range
0x08800000
-
0x01800000
) have a bandwidth of 50MB/s
texture reads from GE memory or VRAM (mem range
0x04000000
-
0x00200000
) have a bandwidth of 500MB/s
if you have a texture in user memory it is possible to load that texture to VRAM at a bandwidth of 150MB/s