Who says clock speed doesn’t matter anymore? IBM has been saying for years, now, that clock speed—a given chip’s gigahertz rating—is no longer the main driver of chip performance.
Other chipmakers are on the same page. Advanced Micro Devices, for its part, has been emphasizing performance per watt or how much work a processor can accomplish per the amount of energy it consumes when discussing its chips. The performance per watt measure is particularly important to businesses whose computer servers can use huge amounts of electricity when massed inside a datacenter. Intel, too, has changed its ways, releasing less-speedy, but far more power-efficient processors such as its Core 2 Duo. This was a major shift for the chipmaker, which said its Pentium 4 would reach 10GHz before changing its direction late in 2004 to focus on energy efficiency and multi-core chips.
But now IBM has unveiled that it will more than double the clock speed of its Power server processor with the forthcoming Power6. Is Big Blue, whose Power5+ chip currently runs at a little over 2GHz, going back on its word? Not exactly. Whereas the Power6 will run much faster, between 4GHz and 5GHz according to what IBM chip designers said at the International Solid States Circuit Conference this week, the processor incorporates several power-saving features, designed to help hold its power consumption level with that of Power5+. IBM is also set to discuss a speedier version of its Cell processor at the ISSCC this week as well.
Power6's energy-throttling features include the ability to scale voltage, and thus move clock speed up or down depending on application load, as well as a low-power state called nap. For Power6, taking a nap means moving into a low-power state that uses about a third of normal power consumption when a server's operating system is idle. Combined, these features are what allow IBM to say that it has held Power6's energy consumption to about the same level as the Power5+ processor. Power5+ processors consume somewhere in the 100-watt range, depending on clock speed and manufacturing process.
Although details are still somewhat sketchy and there have been no independent Power6 tests that I'm aware of yet--more information is likely to become available as IBM gets closer to introducing the Power6 chip later this year--IBM's creation of a chip that's more than twice as fast, yet uses about the same power is a major feat.