Looks like I'm finally being forced down the Virtual PC / win 32 command line mame route
I got the XCode side of it sorted - there was an option to index projects, or some such which was responsible for the 100% cpu. Switching that off made it a whole lot more usable. For some reason, the second time i edited a driver file it behaved as I would expect, so I don't know what was up the first time it decided to recompile everything!
Sadly though, I went in to observe some inputs while playinig a game and discovered that the debugger is flawed on the mac version. Not as flawed as xmame where you can only have one window open at a time, which kinda defeats the object.
Unless I've done yet another thing wrong, it would seem that the game screen doesn't update itself during "animate". This makes it kinda hard to play a game whilst observing memory and registers behaviour!
I compiled up advmame which gave me all the command line goodness and things I wanted, but that was even worse. The debugger came up IN the game window and wouldn't respond to any input apart from the escape key
SO, I'm off to compile up the win32 command line version just to be doubly sure I never dreamt this debugger working properly in the first place!!
If there's a way to resolve the debugger screen updates in macmame then someone please shout as it's by far and away the best option, just not quite there for my purposes
Martin.