You're kidding me.
I remember when I was knee high to an ant, when we had to program seriously tight code to squeeze every last piece of performance out of our 4Mhz chips. Software vendors are facing enough pressures on financial turnaround to want to seriously engage this kind of responsibility especially in the games market; sharehoulders importance far outweighs the environment. And ... Microsoft ... efficient code ... you're kidding me, right?