BAD HARDWARE WEEK

Abstract—In this paper we investigate possible ways to improve the energy ef ciency of a general purpose microprocessor. We show that the energy of a processor depends on its performance, so we chose the energy-delay product to compare different processors. To improve the energy-delay product we explore methods of reducing energy consumption that do not lead to performance loss (i.e., wasted energy), and explore methods to reduce delay by exploiting instruction level parallelism. We found that careful design reduced the energy dissipation by almost 25%. Pipelining can give approximately a 2 improvement in energy-delay product. Superscalar issue, however, does not improve the energy-delay product any further since the overhead required offsets the gains in performance. Further improvements will be hard to come by since a large fraction of the energy (50–80%) is dissipated in the clock network and the on-chip memories. Thus, the efficiency of processors will depend more on the technology being used and the algorithm chosen by the programmer than the micro-architecture.
From:
Energy Dissipation In General Purpose Microprocessors
IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 31, NO. 9, SEPTEMBER 1996

Let me conclude: How Intel will save energy at Yorkfield's 12MB of L3? No way, so they decided to copycat AMD as soon as with Nehalem, unlicenced copy of Barcelona.
Beside, I had no idea that energy efficiency of X86 say depends on software and benchmarks used. Is that why we have recently "only selected" benchmarks allowed?