Popular Mechanics attempts to dispel the ‘MHz Myth’

“At a full gigahertz ahead of AMD, whose Athlon XP processor clocks in at 1.8 GHz, Intel’s line of processors appears to be the faster of the two. However, in test after test, the AMD Athlon chip consistently trumps Intel’s Pentiums. Motorola’s 1.25-GHz G4 chip also more than holds its own against the Pentium,” writes Christopher Allbritton in his article “Chip Primer.” He then goes on to explain the ‘MHz Myth.’

“Microprocessors use ‘pipelines,’ which are electronic paths that bits of data are pushed through as they’re processed by the computer. The length of these pipelines is important to note because longer pipelines are open to more disruptive pipeline hazards. Modern-day processors try to predict the next move of applications, and have gotten very good at doing so. However, mispredicting the next move, while not common, does happen roughly 10 percent of the time,” he writes.

“Chips typically realize their mistakes during the last quarter of the pipeline, so the longer the pipeline, the longer it takes to flush the message from the pipeline and fix the problem. As a result, performance suffers. With AMD’s 10-stage pipeline and Motorola’s 7-stager, if there’s a mistake in the last quarter of the pipeline, it’s not as big a deal to flush out the whole pipeline and start anew. On the flip side, you can see how Intel’s 20-stage pipeline would lead to inefficiency. This explains why a 1.25-GHz Power PC G4 chip can be competitive with a 2.5-GHz Pentium 4,” says Allbritton.

Despite a few mistakes, including “Power PC G3’s [top out at] 600MHz,” it’s an interesting read and goes a long way to explaining the little saying we use when talking about Pentium’s; we’ve seen shorter pipelines in Alaska. Read the article here.

Reader Feedback

This site uses Akismet to reduce spam. Learn how your comment data is processed.