PC Watch (my translation): PS3 Evaluation System, and much,

[PC-Engine]

Just like they did with PS2, by leaving T&L out of the GS, their "vertex shaders" (the VUs) run at 300MHz instead of 150MHz. Without considering the fact that they were also much more interesting units than Vertex Shaders themselves.

I think PS2's design philosophy was a bit different. Back in those console days the CPU still did the TnL. Also the GS with all that eDRAM was already a big chip so it would've been inmpossible to add on a TnL unit that's why in the end you had the VUs on the EE.

 

[jvd]

If it is true that most of RSX is dedicated to pixel shading, then PS3 won't have a problem dedicating one or two SPEs to handle geometry to help RSX. It's almost like Sony wondered what would be better between a VS running at 500MHz or a VS-like-unit that runs at 3.2GHz.

Tons of questions though . How many triangles are the spe's going to output ?

Did they make the right choice ? HOwever I highly doubt they juts chopped out the vertex shaders .

Just like they did with PS2, by leaving T&L out of the GS, their "vertex shaders" (the VUs) run at 300MHz instead of 150MHz. Without considering the fact that they were also much more interesting units than Vertex Shaders themselves.

The gs was being designed in 1996-1998 , the first tnl gpu came out in 1999 and i'm sure that for 1999 sony made a good choice as the tnl gpus of the time weren't all that advanced .However there are alot of other features missing out of the graphics card that evne the tnt 1 had .

I"m sure in the end the programers and developers did things with the cpu that sony never thought of . But they also had to spend alot of time reinventing the wheel so to speak .

 

[DemoCoder]

Nowadays, the pixel shaders do most of the "L" part of TnL. Per-pixel lighting is replacing per-vertex. With topology processing and more complex shading algorithms coming into play, the traditional VS isn't flexible enough anyway.

 

[London Geezer]

If it is true that most of RSX is dedicated to pixel shading, then PS3 won't have a problem dedicating one or two SPEs to handle geometry to help RSX. It's almost like Sony wondered what would be better between a VS running at 500MHz or a VS-like-unit that runs at 3.2GHz.

Tons of questions though . How many triangles are the spe's going to output ?

Did they make the right choice ? HOwever I highly doubt they juts chopped out the vertex shaders .

That was my question too. Though i'm pretty sure they'll fare quite well. My worry is the bandwidth between Cell and RSX, which is bound to be much lower than the bandwidth you'd get if the geometry was calculated all inside the RSX.

I do have a feeling that keeping all dynamic geometry of a scene/frame on Cell, the geometry can interact better with animation and physics, being all on the CPU.

 

[Titanio]

Just like they did with PS2, by leaving T&L out of the GS, their "vertex shaders" (the VUs) run at 300MHz instead of 150MHz. Without considering the fact that they were also much more interesting units than Vertex Shaders themselves.

Did they make the right choice ? HOwever I highly doubt they juts chopped out the vertex shaders .

To clarify, they haven't, if RSX is the same config as G70, of course. There'd be 8 vertex shaders there. But when you look at how much processing their doing, if you look at Gflops, about 85% of the programmable power in RSX is with the pixel shaders.

I'd venture to guess that for most games, the VS in RSX would be enough. What I was addressing was the rarer situation where more would be needed.

My worry is the bandwidth between Cell and RSX, which is bound to be much lower than the bandwidth you'd get if the geometry was calculated all inside the RSX.

Geometry that changes from frame to frame, due to collision detection etc. has to be passed across from CPU to GPU anyway..(and geometry has to be passed back from the GPU too for collision detection/physics).

 

[sklaar]

http://ps3.ign.com/articles/636/636848p3.html

good summary