Phalanx said:
Here's how the TEV works: There is one pipeline that can handle up to 16 texels. This is a significant departure from the standard pipeline configuration of most nVidia and ATI chips.
The XBox1 gpu had 4 pipelines that could render 4 texels each. If a pixel had 4 layers, one pipeline could process it all in one clock cycle. If it had 5, it needed two clock cycles. If you had 4 pixels, each with 4 layers, it could render that in one cycle. If you had 1 pixel with 2 layers, 1 with 4 layers, one with 2 layers and another with 5, it would do the first 3 in one cycle, but have to process the last one in two. If you had 16 pixels with only 1 layer, it would take 4 clock cycles to process them all.
Here's a breakdown:
Scenario A) Pixel 1(4 layers) + Pixel 2(4 layers) + Pixel 3(4 layers) + Pixel 4(4 layers) = 1 clock cycle (16 layers)
Scenario B) Pixel 1(2 layers) + Pixel 2(4 layers) + Pixel 3(2 layers) + Pixel 4(5 layers) = 1 clock cycle for first 3 pixels, 2 for the 4th pixel (11 layers)
Scenario C) 16 Pixels (1 layer each) = 4 clock cycles
Let's look at the same scenarios with the TEV.
Scenario A) Pixel 1(4 layers) + Pixel 2(4 layers) + Pixel 3(4 layers) + Pixel 4(4 layers) = 1 clock cycle (16 layers)
Scenario B) Pixel 1(2 layers) + Pixel 2(4 layers) + Pixel 3(2 layers) + Pixel 4(5 layers) = 1 clock cycle (11 layers + room for 5 more layers)
Scenario C) 16 Pixels (1 layer each) = 1 clock cycle
TEV can do 16 layers regardless of how many pixels they are in.
The only advantage the XBox1 gpu had was a better geometry engine and programmable shaders. Now, from what I have heard, Wii's gpu doubles this number, and has a higher clock speed. Not to mention increased memory. Sure, Wii doesn't have programmable shaders, but that doesn't mean it's less powerful than the original xbox. A NASCAR vehicle doesn't have air-conditioning or power door locks, but does that mean it's less powerful than a fully loaded Camry? Of course not. You have to look at the whole picture. --------------------------------------------------------------- Legend11: The reason that most multiplatform games looked better on the xbox is because the shader routines were included in the SDK and didn't need to be written. Most developers were too lazy to take the time to figure out how to properly utilize the TEV unit. |
This is a little off. The Xbox GPU could process 4 textures in one pass, but not in one clock cycle. It had 4 pipelines, and each pipeline could process two stages in a single cycle, with up to 4 stages in one pass. Additional stages would require an additional pass, meaning the polygons need to be T&L'd again. The Gamecube's TEV had 4 pipelines capable of processing one layer per pass, but up to 8 stages in a single pass. The Wii extends this to 8 pipelines and 16 stages in a single pass.
