Thanks for all your inputs!
I have some new findings. I made a simple program to move a textured front facing quad along the z axis so I can see the transition in mipmap level has they occur (Min filter set to LINEAR_MIPMAP_LINEAR).
My texture is a 256x256 DXT1, and all the levels are filled up with data. In addition, I made sure to put distinctive colors in the levels so I can really the mips. I am using glCompressedTexImage2DARB and the texture data comes from a pixel buffer object (glBufferData…).
With my Radeon 4670, I noticed that the first level of the texture is loaded and appears fine. But I get black in all the other levels. I can see the fist mip blend into black as my quad moves away.
It was when I decided to load the textures mip levels without using the PBO that I started getting something. All the mip levels loaded fine and I could see them transition on my quad as I move it.
Going to my original post, now changing the value for GL_TEXTURE_BASE_LEVEL works fine on my Radeon.
So it seems my problem was with the pixel buffer object. The first mip level loads fine but all the other don’t. However, I know that it works fine on my geforce.
I wonder if there is something special about loading textures through pbo on radeon…