On some cards, the textures don't need to be a power of 2 either. On some they only need to be a power of two wide. On some they have to be square.
TextureWidth and TextureHeight are your friends, and the documentation includes an incredibly useful example for determining the texture abilities of any given card.
TextureWidth and TextureHeight are your friends, and the documentation includes an incredibly useful example for determining the texture abilities of any given card.