OpenGL 1.1.3+ and 8-bit offscreen rendering

I have a question for anyone familiar with recent implementations of OpenGL
for the Mac. I am currently unable to get aglChoosePixelFormat to work when
trying to specify an 8-bit offscreen renderer as follows:

AGLPixelFormat pixelformat;
GLint attrib[] = { AGL_RGBA, AGL_PIXEL_SIZE, 8, AGL_OFFSCREEN,
AGL_NONE };

pixelformat = aglChoosePixelFormat( NULL, 0, attrib );

aglChoosePixelFormat always returns NULL so long as I specify 8-bit and
offscreen.

Has anyone else encountered this? Is Apple aware of this change, and was it
intentional?

Thanks,

==
Yu-Hong Wang
yhwang@maplesoft.com

[DJ Tricky S]

what if you don't specify the AGL_RGBA attribute flag? You're not using an 8-bit pixel for an RGBA texture are you? I doubt that the hardware supports this.