Second, smaller processor sizes reduce power consumption. The number of transistors each core has and the amount of silicon real-estate they take up determines the amount of power the core uses – smaller processors have fewer transistors and thus use less power than larger processors. In a dual-core chip, the total number of transistors is greater than it is in a single-core chip, but each core has fewer transistors, making it more power efficient.
Third, some of the processor functions, such as controlling memory, can be shared between cores, so that each core consumes less energy by not performing a redundant task.
So transitioning to a multicore architecture is an obvious way to save power, and both Intel and AMD have done so. But they’re looking at other ways to create efficiency. As Pawlowski explains, managing processors at the circuit and individual transistor level can also save power. For instance, specific circuits on a transistor are designated to control the manipulation of a photo or to play a DVD. When that circuit needs to be used, the transistors that comprise the circuit are turned on with a certain voltage. In a perfectly efficient chip, those transistors would turn on and off only when they’re needed. However, even when a circuit is idle, its transistors are using a small voltage that slowly leaks out of the transistor, says Pawlowski. This leakage produces heat and wastes electricity.
While there is much overlap in the ways that AMD and Intel are approaching this problem of waste and leakage at the circuit level, their solutions are different. Intel is working to solve the problem by designating “sleep transistors” on a chip to micromanage the circuits in each core. These transistors completely turn off the voltage to transistors in circuits that are dormant.
AMD also puts portions of the processor to sleep, explains McGrath; but it does so by having an algorithm instruct the processor to go into various levels of sleep, by shutting down its clock speed so that standby computations aren’t carried out as quickly. The algorithm “can ask a part to go into its lowest power state,” he says, “there are five or six of these power states that are used depending on the load of the processor.”
Intel has announced prices for its new energy-efficient chips – they’re less expensive than AMD’s current offerings, which will put pressure on its rival. For Intel, though, the test of whether its power-saving chips can compete well against AMD’s offerings won’t come until its new processors hit the market.