Since yesterday, my 2008 Mac Pro has no sound. The startup chime is silent. No sound comes from the speakers and the line out/in options in system sound preferences is missing, although it still lists my Logitech webcam microphone. Could the sound chip on the logic board have stopped working? The missing line in/out devices in the sound preferences seems like it might be a hardware problem. I have tried all of the normal things like checking cables and resetting pram but no change.