 | By Ian “Gizmo” Richards Today’s PC-purchaser can choose to buy up to a quad-core processor, and soon this choice will extend to eight or more cores. These multicore processors seem to offer the potential for greatly improved performance, but you may not get the speed you expect. |
The multicore-processor revolution is here
Until about five years ago, each new generation of microprocessors offered increased power through faster clock speeds. However, when processor speeds moved into the 3GHz region, the heat generated by these fast single-processor chips became a serious barrier to further speed improvements.
Chip manufacturers responded by producing CPU chips comprised of multiple processing units (cores), each of which runs at a slower speed. In lieu of a single processor running at 3.3GHz, for example, these new chips might have two cores running at 1.6GHz — with significantly less heat output than that of a single, faster processor.
CPU vendors boasted that this approach would allow them to produce future processors with ever-larger numbers of cores. Intel, for instance, talked of processor designs with 64 or more cores.
This change in CPU design may create a certain amount of confusion. For example, clock speed used to be a reasonable performance indicator: a 3GHz CPU could reasonably be assumed to be faster than a 2.5GHz unit. But with multicore chips, clock speed is now only one of several factors that determine actual processor performance.
The limits of parallel processing
The idea that two processing cores are twice as powerful as a single core lacks validity for processing tasks that are strongly sequential in nature. Unfortunately, that describes most computer processing.
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