OpenGL newbie seeks help!

Hey /prog/, I'm writing a cross-platform OpenGL application which does some off-screen rendering. I've found two ways of doing that - with pbuffers and with FBOs, the latter is preferable. I want old videocards to be supported too.
Now tell me, which technique should I use? Do the older videocards support FBO? Do they support pbuffers?
Thanks.

>>14
The framebuffer pointer paradigm is utterly inefficient and definitely doesn't give you access to "raw machine power”.
It should be made efficient. Because it is easy to use.