One of our popular computer books is Greening IT
by various authors and contributors of Internet books - here is a snippet: 'This change in the hardware status quo changed the software paradigm as well. Rather than sharing software stored on a central mainframe computer, individual users enjoyed individual copies of software applications installed on each personal computer. Because each user ran software on his/her own dedicated PC this new model of computing avoided the difficulties of dividing CPU-time among multiple simultaneous users attempting to share one mainframe CPU. This evolutionary stage draws direct parallels with the stage in the power generation industry’s evolution characterised by improvements in generator design and architecture.'