The ever advancement of processors are simply gobbled-up by the demands of the latest bloatware and ever higher level languages like Java.
If you had actualy used Java you would have known that it's recieved quite a few performance boosts in it's lifetime (First in version 1.3, then in version 1.5). Running the same Java code, compiled by Java 1.5 and 1.2 the 1.5 version will be running circles around the 1.2 version. Mac? Pretty sure it was PC, I got a 10min demonstration of it (150mb MPEG file) on one of my discs somewhere...., and I got it from a PC Gamin mag (back before I had net access).
Until they where 'aquired' by Microsoft, Bungie was primarilly a Mac developer. Sure a PC version was planned (like with Marathon) but was never demonstrated. Went right from Mac to XBox.