A Question about the X800

[Unknown Soldier]

Hi Dave

I see the X800 has 12 pipes but the textures per pass is 16. Is this right? Shouldn't it be 12 textures per pass?

Thx
US

 

[tEd]

16 is right for r9500/x300 and up or for any ps2.0 capable chip

 

[Dave Baumann]

16 textures per pass related to the number of texture layers can be applied to a single pixel (8 in fixed function, 16 under PS2.0)

 

[Tim]

Hi Dave

I see the X800 has 12 pipes but the textures per pass is 16. Is this right? Shouldn't it be 12 textures per pass?

No, textures per pass is not the same as a textures per cycle. Each pass can take multiple cycles. With 16 textures a pass is actually 16 clock cycles as the R3xx/R4xxs only can do one texture operation per pipe per cycle. All R3xx/R4xx GPUs can do 16 textures per pass.

 

[Unknown Soldier]

k.. thx

US

 

[NeoCool]

I thought DX8 cards and below could only do 4 texture accesses? Hmm, must've read wrong.

 

[Ostsol]

I thought DX8 cards and below could only do 4 texture accesses? Hmm, must've read wrong.

Sorta. The fixed function pipeline appears limited to the number of pixel pipelines, and PS1.1-1.3 allows up to 4 texture samplers per pass. PS1.4, however, allows 6.

 

[OpenGL guy]

I thought DX8 cards and below could only do 4 texture accesses? Hmm, must've read wrong.

Sorta. The fixed function pipeline appears limited to the number of pixel pipelines, and PS1.1-1.3 allows up to 4 texture samplers per pass. PS1.4, however, allows 6.

I think the corelation between fixed function texture stages and pixel pipelines is purely coincidental. The X300 has 4 pixel pipelines yet can handle 8 fixed function texture stages (I believe that 8 is the maximum allowed by DX9). Also, didn't the Kyro support 8 fixed function texture stages?

 

[DeanoC]

Yep Kyro has 8 texture passes back in Dx7

 

[Ostsol]

Hmm. . . Wierd. I might actually be wrong about the R200, too. Unfortunately, I don't have mine anymore to test.

 

[NeoCool]

The 6 texture access capable R200 sounds right to me, I remember reading that somewhere. I think DX7 cards though, like the GeForce 1 (or 256) / 2 / Radeon 7xxx, can only go up to 2 texture accesses..... or may be that's only the GeForce 2 MX / 4 MX series.

 

[tEd]

gf/2mx -> 2
r7xxx -> 3

 

[Ostsol]

The 6 texture access capable R200 sounds right to me, I remember reading that somewhere.

Well, I know that it's 6 for PS1.4, but I'm not sure about the fixed function pipeline.

 

[mczak]

The 6 texture access capable R200 sounds right to me, I remember reading that somewhere.

Well, I know that it's 6 for PS1.4, but I'm not sure about the fixed function pipeline.

At least in OGL it can do 6 with the fixed function pipeline (and 8 would be the API limit).

 

[Ostsol]

Hmm. . . It's kinda strange that the API limit would be 8, since OpenGL has tokens for 32 texture units.

 

[mczak]

Hmm. . . It's kinda strange that the API limit would be 8, since OpenGL has tokens for 32 texture units.

You're right, API limit is 32. I must have confused that with something else...