Latest 360 slims feature SoC

Better efficiency and less heat
Of course, the move to the SoC allows Microsoft to reduce cost, but it also greatly reduces heat and increases power efficiency; these are two areas that Microsoft has been improving with each generation of Xbox 360 that has been released.
The 372 million transistors that make up the new SoC chip that Microsoft has developed took the company 5 years of research and development to make happen. Microsoft has paid special attention to guaranteeing compatibility, and to this end has implemented precision latency and bandwidth throttling that perfectly impersonates the older Xbox systems which used separate chips to make up the console.