How much textures could the wii fit due to compression?

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The wii is suppose to be a gamecube upgraded in terms of graphically capabilites. So it has the same option to compress textures that wouldn't fit in it's ram? Right? I belive the gamecube allowed for 6 times more textures due to this compression. For example 18mb of ram for textured really was the equivalent to 108mb. So does anybody know if it's the same for the wii, or more? I need to know for my  analysis I'm making of the wii's graphical capabilities, but can't find anything about it.