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Lord_Of_NoTiNg · Jun 15th, 2002, 10:38 AM

Now let's take a look at how Microsoft got the idea that their graphics chip can do 125 million polygons...
The PS2's Graphics Synthesizer has the highest pixel fill rate of the next generation of consoles. Most remeber the 4.0 GPixels on Microsoft's spec comparence sheet. Well, Microsoft was nice to include a "(anti-aliased)" next to it. What does "4.0 GPixels (anti-aliased)", mean? It's misleading. The Xbox has hardwired 4x FSAA, when this is turned on the actual total of 1.0 GPixels is re-rendered 4 times to remove aliasing. Another possible reason for Microsoft to say Xbox's fill-rate is 4 GPixels per second. Is that the 1 GPixels is with 2 texture layers, if it is NOT used Xbox would not gain any performance and if it is used Xbox wouldn't lose any performance. It remains 1.0 GPixels w/ 2 textures, so what MS possibly did was it doubled the fill rate twice. Trying to compare it to PS2's fill rate w/ no texture. What MS did was it came up with misleading numbers. The Xbox can't go higher than 1 GPixels per second.
The NV2a in the Xbox has 4 pixel units running at 250 MHz, that's 1 billion pixels/second. While the GS in the PS2 has 16 pixel units running at 150 MHz, which is 2.4 billion pixels every second.
Now let's talk about polygons. Right here I'm talking about polygon rendering and not polygon transformations. To calculate polygon rendering performance, you take the pixel fill rate, and write it in millions. So PS2s pixel fill rate is 2400 Million. When Sony says polygons, it is referring to 32 pixel polygons. Divide 2400 Million by 32. You get 75 Million (32-pixel) polygons per second. That is raw and doesn't include textures, they use up pixels also. Now let's take Microsoft's alleged pixel fill rate of 4000 Million, which MS has on it's spec sheet and divide it by 32, you get, yes you guessed it, 125 Million (32 pixel) polygons per second. Here's the problem, the NV2a doesn't have a 4000 M fill rate but a 1000 M fill rate. So it's 31 Million (32 pixel) polygons per second. This isn't raw, since there's also 2 texture units for each pixel unit. So that's 31 million with 2 texture layers, the PS2 is around 38 Million with 1 texture layer and 20 million with 2 texture layers. The Xbox maxes out at 31 MPolygons per second, if textures aren't placed on those polygons- Xbox will not gain a polygon rendering increase in performance. The PS2's Graphic Synthesizer could render 75 MPolygons per second with no texture. The NV2a in the Xbox can't render higher than 31 MPolygons per second at all.
Okay now take that all into account and then check out the following...
"Is the XBox graphics chip the same as a GeForce 3 card? Not quite. The NV2A chip that powers the XBox is quite similar to the GeForce 3, but isn't quite a GeForce 3. The GeForce 3 is a 64mb card with 350mhz RAMDAC. The XBox's NV2A is a card that SHARES it's memory with the XBox's system RAM and has a 250mhz RAMDAC. The NV2A compensates for this by having a Second Vertex Shader, as opposed by the GeForce 3's single vertex shader. However, Microsoft claims that this second vertex shader instantly bumps the XBox's theoretical max poly count from the 31 million that Nvidia lists for the GeForce 3, all the way up to 125 million pps. According to most experts, the area that will actually see the most improvement from this will actually be in Bump Mapping. Microsoft has yet to explain how the second vertex shader yields an additional 94 million polygons per second."
I don't know enough to go more in detail about this but this is definitely an interesting point, and either way you turn it, it doesn't seem like the XBox has the advantage here.

I can understand that this is all a bit confusing if you're not a real tech-freak. It comes down to this: when developers have learned how to use the power of the PS2 GS properly they'll get a lot more out of it than XBox developers will get out of the XBox GPU. The PS2 GS combined with the EE can do a lot more advanced visual effects than the XBox GPU combined with its CPU.

Please don't close this thread down.
I just want people to read the thread not to post anything.

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Jun 15th, 2002, 10:38 AM	#2
Lord_Of_NoTiNg CheeseAndBreadGuy Joined: Mar 2002 Age: 36 Posts: 50	Now let's take a look at how Microsoft got the idea that their graphics chip can do 125 million polygons... The PS2's Graphics Synthesizer has the highest pixel fill rate of the next generation of consoles. Most remeber the 4.0 GPixels on Microsoft's spec comparence sheet. Well, Microsoft was nice to include a "(anti-aliased)" next to it. What does "4.0 GPixels (anti-aliased)", mean? It's misleading. The Xbox has hardwired 4x FSAA, when this is turned on the actual total of 1.0 GPixels is re-rendered 4 times to remove aliasing. Another possible reason for Microsoft to say Xbox's fill-rate is 4 GPixels per second. Is that the 1 GPixels is with 2 texture layers, if it is NOT used Xbox would not gain any performance and if it is used Xbox wouldn't lose any performance. It remains 1.0 GPixels w/ 2 textures, so what MS possibly did was it doubled the fill rate twice. Trying to compare it to PS2's fill rate w/ no texture. What MS did was it came up with misleading numbers. The Xbox can't go higher than 1 GPixels per second. The NV2a in the Xbox has 4 pixel units running at 250 MHz, that's 1 billion pixels/second. While the GS in the PS2 has 16 pixel units running at 150 MHz, which is 2.4 billion pixels every second. Now let's talk about polygons. Right here I'm talking about polygon rendering and not polygon transformations. To calculate polygon rendering performance, you take the pixel fill rate, and write it in millions. So PS2s pixel fill rate is 2400 Million. When Sony says polygons, it is referring to 32 pixel polygons. Divide 2400 Million by 32. You get 75 Million (32-pixel) polygons per second. That is raw and doesn't include textures, they use up pixels also. Now let's take Microsoft's alleged pixel fill rate of 4000 Million, which MS has on it's spec sheet and divide it by 32, you get, yes you guessed it, 125 Million (32 pixel) polygons per second. Here's the problem, the NV2a doesn't have a 4000 M fill rate but a 1000 M fill rate. So it's 31 Million (32 pixel) polygons per second. This isn't raw, since there's also 2 texture units for each pixel unit. So that's 31 million with 2 texture layers, the PS2 is around 38 Million with 1 texture layer and 20 million with 2 texture layers. The Xbox maxes out at 31 MPolygons per second, if textures aren't placed on those polygons- Xbox will not gain a polygon rendering increase in performance. The PS2's Graphic Synthesizer could render 75 MPolygons per second with no texture. The NV2a in the Xbox can't render higher than 31 MPolygons per second at all. Okay now take that all into account and then check out the following... "Is the XBox graphics chip the same as a GeForce 3 card? Not quite. The NV2A chip that powers the XBox is quite similar to the GeForce 3, but isn't quite a GeForce 3. The GeForce 3 is a 64mb card with 350mhz RAMDAC. The XBox's NV2A is a card that SHARES it's memory with the XBox's system RAM and has a 250mhz RAMDAC. The NV2A compensates for this by having a Second Vertex Shader, as opposed by the GeForce 3's single vertex shader. However, Microsoft claims that this second vertex shader instantly bumps the XBox's theoretical max poly count from the 31 million that Nvidia lists for the GeForce 3, all the way up to 125 million pps. According to most experts, the area that will actually see the most improvement from this will actually be in Bump Mapping. Microsoft has yet to explain how the second vertex shader yields an additional 94 million polygons per second." I don't know enough to go more in detail about this but this is definitely an interesting point, and either way you turn it, it doesn't seem like the XBox has the advantage here. I can understand that this is all a bit confusing if you're not a real tech-freak. It comes down to this: when developers have learned how to use the power of the PS2 GS properly they'll get a lot more out of it than XBox developers will get out of the XBox GPU. The PS2 GS combined with the EE can do a lot more advanced visual effects than the XBox GPU combined with its CPU. Please don't close this thread down. I just want people to read the thread not to post anything.