Complete lock up while playing

[Urkle]

It actually is because the apple drivers are old, and that card is on the bottom rung of supported video cards. The OpenGL drivers in leopard are only at 2.0 for SOME cards. And really Amnesia needs 2.1 which is provided only by snow leopard and higher. Also Amnesia is using some more advanced functionality that probably every other PPC game you have aren't using.. Specifically Occlusion queries, and a LOT of them.

As I was testing on 17" version of your powerbook it would continually run into infinite loops in the game due to the occlusion queries results just wouldn't return.

Unfortunately Apple has nailed the coffin on PPC Mac's, there just isn't much that can be done. There are bugs in their snow leopard drivers they just plain don't want to fix (e.g. improperly implemented GLSL specifications, BAD performance on Nvidia 7300 cards). Things have improved since Steam for Mac came out, but it's only affected things a little on snow leopard and a significant amount on lion (Lion finally implements OpenGL 3.2, even though the latest is 4.2)