Sapphire's special version of the X800 GTO is called X800 GTO². As you can see in the following picture it uses an R480 core, which is also used on the X850 Pro, XT and XT PE.
The GTO² is a special product from Sapphire only. Neither the regular GTO, nor the GTO Ultimate use the unlockable chips. If it does not have ² in the name, it can't be unlocked.
UPDATE: The X800 GTO cards from Connect3D can also be unlocked, see page 4 of this article.
The GTO² comes with 12 pipelines enabled by default, but the only lock which limits it to this number of pipelines is located in the Bios.
No cards with defective pipelines have been found yet, which means (so far) the success rate is 100%.
An AGP version of this card does not exist. Some shops list a Sapphire GTO² AGP but this is not a Sapphire product, it's probably regular GTO's which are labeled "wrong".
The mod presented here allows to unlock your X800 GTO² to run at 16 pipelines.
