Ok, got one of these coming to me in the post at the moment (thankyou Scan ).
XFX 256mb AGP 6800XT - 300/700 8 pipes, 5 vertex
It seems that you can unlock up to 8 pipelines and an extra vertex shader (basically the reason i got it - cheap 6800 with the possibility to get to near GT speeds with no extra cost).
From browsing other forums, it appears that most people can unlock 4 pipes, but not all 8. Is there something in the architecture that stops the card from handling odd numbers of pipes? e.g i've never seen anyone say that they managed 15 pipes unlocked.