Rags: I'm not saying we couldn't use more memory/FSB bandwidth, only that video memory bandwidth is the major limitation. The p4's strength is certainly in it's platform, not the cpu. However, I like to play quake3 with all the details on at 800x600. I'd go higher if I could and I'd kill for FSAA. Turn that all on though and I'd get probably less than 5 fps, and it wouldn't matter if I had a k6-2 300 or a p4 overclocked to 2 ghz, I'd still get 5 fps because the limitation is the video memory.
DGhost: I'm assuming you're referring to the following paragraph:
You'll notice that nowhere does it say that the kyro has a depth (or z-)buffer, only that it does away with it. It does say it does HSR and depth-testing on-chip, however that does not mean it has a depth buffer.
The depth buffer on all of today's cards are external (from the GPU) - but it's still on the video card in the video memory.
actually, I did see later on they said '[provides] a depth buffer on-chip'. They are wrong. If it truly did have a depth buffer, then there would be no need for the work around they described on the same page..
You are right about the PCI speed though. I don't know where that 512 number came from. AGP 2x, which has been around for something like 4 years now, does have 512mb/s of bandwidth. It can handle that transfer speed of 240 mb/s. Although I'm sure after optimization, you could lower it enough that the PCI bus could do it too.
DGhost: I'm assuming you're referring to the following paragraph:
<font face="Verdana, Arial, Helvetica" size="2">
Since depth-testing and hidden surface removal are implemented entirely on-chip, an external depth buffer has been dispensed with. In contrast, GeForce accesses external, or off-chip, memory for depth-testing. Another important difference between Kyro and GeForce is the order in which depth-testing takes place. Kyro performs depth-testing and hidden surface removal prior to texturing. As only visible pixels are textured, the savings in texture bandwidth is a function of the extent of overdraw. GeForce performs depth-testing after textures have been applied to the polygon.
</font>
Since depth-testing and hidden surface removal are implemented entirely on-chip, an external depth buffer has been dispensed with. In contrast, GeForce accesses external, or off-chip, memory for depth-testing. Another important difference between Kyro and GeForce is the order in which depth-testing takes place. Kyro performs depth-testing and hidden surface removal prior to texturing. As only visible pixels are textured, the savings in texture bandwidth is a function of the extent of overdraw. GeForce performs depth-testing after textures have been applied to the polygon.
</font>
The depth buffer on all of today's cards are external (from the GPU) - but it's still on the video card in the video memory.
actually, I did see later on they said '[provides] a depth buffer on-chip'. They are wrong. If it truly did have a depth buffer, then there would be no need for the work around they described on the same page..
You are right about the PCI speed though. I don't know where that 512 number came from. AGP 2x, which has been around for something like 4 years now, does have 512mb/s of bandwidth. It can handle that transfer speed of 240 mb/s. Although I'm sure after optimization, you could lower it enough that the PCI bus could do it too.
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