Our second source went on to explain that the "Gamecube 1.5" moniker, while accurate, doesn't mean that gamers won't see graphical improvements on the Wii. "There are three main differences which will result in graphics improvements. One, the increased memory clock speed, from 162 megahertz to 243 megahertz, means that it is easier to do enough pixels for 480p mode versus 480i. Two, the enhanced memory size of the Wii gives much more room for image-related operations such as anti-aliasing, motion blur, etc. The performance to these memory systems from the graphics chip is also improved. So full-screen effects and increased texture usage seem likely as a result."
The same source cited a third factor: an apparent increase in fixed-function "texture environment stages"--also known as TEV stages--from 8 in the Gamecube to 16 on the Wii. (The source stressed "apparent" because this feature wasn't described in the Wii's graphics overview documentation--which was simply repurposed from the Gamecube--but it was listed among the Wii's programming calls. "Assuming this isn't a bug, it means that much more complex per-pixel graphics operations are possible," our source told us. "However, each additional TEV stage use slows down the graphics chip more and more, so it is a trade-off. You can do more powerful pixel operations and you'll bottleneck the chip and not be able to do as many of them, nor as many vertex operations (since the pixel and vertex systems are tightly coupled on fixed-function graphics chips.) Eight additional stages mean more complex operations are possible. It would be easier to do bump mapping perhaps, or environment mapping, but you would have to get creative with how you do it. It wouldn't be easy.
That assessment dovetailed with what we heard from our first source. "Almost all the shader effects on PC, Xbox 360 and PS3 can be reproduced on the Wii by re-implementing them with the fixed function hardware of the Wii's GPU. Most games just port the effect over. A few teams have gone as far as making a shader-to-Wii conversion tool. It reads the shader code and generates the fixed function code necessary to achieve the same result. Keep in mind that the Wii's GPU is not as fast or feature rich as the Xbox 360 or PS3, but that doesn't mean you can't get very close results."