"I don't think they(Windows Vista vs. OS X)'re equally flawed - I think Leopard is a much better system," he said. "(But) OS X in some ways is actually worse than Windows to program for. Their file system is complete and utter crap, which is scary."

...He said he finally saw Linux as able to boast genuine green credentials, after years of hard work.

He and fellow programmers modified almost every part of the operating system's core to improve power management. They also enhanced the ability to track down the most power-hungry parts of a hardware and software system.

"Everybody wants to be power-aware," he said. "It's not just that you want to be green - it's eating up your batteries."