AMD Corporate Fellow Sam Naffziger published a new whitepaper that provides an update about 25x20, the company's initiative to increase energy efficiency 25-fold by 2020. The paper discusses the benefits of hUMA (Heterogeneous Unified Memory Access) and HSA, as well as the slowing rate of power improvements enabled by process node shrinks. He also discusses AMD's efforts on Adaptive Voltage and Frequency Scaling (AVFS), you can read a distilled version at ExtremeTech.
After years of promises from AMD with precious little to show for the company’s CPU efforts (unless you count the collapse of its core business as a victory), enthusiasts are understandably skeptical about what Carrizo will offer. The good news on this front is that AVFS isn’t just an idea AMD pulled out of its hat. It’s an understood tradeoff that adds design complexity on the chip, but can help compensate for foundry variation, and is generally believed to improve power consumption by at least the 20% figure that AMD is claiming. Some publications claim benefits up to 45% depending on workload (bear in mind that these are very different chips and target markets).