Lainatun viestin kirjoitti alkujaan Hex
Mielellään kuulen perustelusi, että grafiikkamuistin kaksinkertaistaminen tekisi PS2:sta Xboxia "paljon tehokkaamman". Muutenkin selitys, että sillä hetkellä oli tyydyttävä liian pieneen muistiin ontuu. Jos näin on, on syy väärän arkkitehtuurin valinnassa, ei liian kalliissa muistissa. Kun vanha Dreamcast teksturoi paremmin, ei huonommalle suorituskyvylle voi olla kunnon syitä.
No jaa, kyllä taitaa Dreamcast jäädä aika mukavasti PS2:lle.
FPS = 30, 3 million polygons per sec.
640*480*32-bit render buffer = 1228800 bytes
640*480*16-bit display buffer = 614400 bytes
640*480*32-bit z-buffer = 1228800 bytes
PS2 Total = 3072000 bytes
Memory left for texture cache = 1122304 bytes
DC internally renders at 32-bit and can dither before writing to the local memory. Assuming a 3 meg display list and 640*480*16-bit dual buffers. DC Total = 4374528 bytes
Memory left for textures = 4014080 bytes
For texture format let's compress 24-bit 256*256 textures using PowerVQ and 8-bit CLUT. So that's 2-bits/pixel for DC and 8-bits/pixel for PS2.
Using PowerVQ:
256*256*2-bits/pixel / 8-bits/byte = 16384 bytes
Look-up table = 3bytes*4*256 entries = 3072 bytes
Total = 19456 bytes
Using 8-bit CLUT
256*256 = 65535 bytes
CLUT = 3*256 = 768
Total = 63488 bytes
PS2 has 32 MBs main memory and DC has 16 MBs, so let's store all textures in local memory on DC and on the PS2 let's use 16 MBs for textures. At 30 fps, the PS2 can transfer all 16 MBs/frame and the DC can texture from all of the textures in local memory.
# of PowerVQ 24-bit 256*256 textures in local RAM on DC:
4014080 / 19456 = 206 256*256 textures
# of 8-bit CLUT 24-bit 256*256 textures in main RAM on PS2:
16*1048576 / 63488 = 264 256*256 textures
Keep in mind that the PS2 streams textures into local memory from main RAM, so the comparison between using local memory for DC and main RAM for PS2 is fair.
So as you can see, under your conditions of "both using frame buffers of the same resolution, color depth, and z-buffer accuracy, both displaying compressed textures of the same color depth and resolution, both using their respective native compression (CLUT for PS2 and PowerVR VQ for DC)" the PS2 can edge out the Dreamcast. I could have used 4-bit CLUT in my example and the PS2 would surpass the Dreamcast in textures per frame even more.
It's taken me a while to write this and I just saw your latest post. The problem is you keep on comparing DC's 8 MB VRAM with PS2's 4 MB embedded RAM, and they are not directly comparable. With dynamic texturing on the PS2, a better comparison with regards to textures per frame is DC's 8 MB VRAM versus PS2's 32 MBs main RAM.
So, what the PS2 can actually display more textures per frame than the DC, under similar conditions!!!
Ars Technican foorumeilta. En jaksa kaivaa linkkiä mutta siellä ne on. Siitä vaan hakemaan jos et muuten usko.
