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Do Newer Processors Equate to Slower Applications? : Page 3

While the promise has been that with new computers come more power and faster overall performance, it's likely that the speed is about to hit a brick wall. Even better, individual core speeds might be slowing down.


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Every Last Drop
Intel recently announced that it was switching to a different substance called halfium that would allow for another decrease in size. This decrease, however, will be limited. At this point just like squeezing blood from a turnip, the processor engineers are squeezing speed from silicon-based processors. It is simply not physically possible to go much smaller—thus much faster—with the current silicon structure.

In addition to shrinking the transistors—which can't get much smaller, if any—you can also shrink the infrastructure around the transistors. However, shrinking the infrastructure will mean only a minor gain in speed, leaving only the cache as an area where some speed gains can still be found, but even there only minor gains are expected.

Building processors is a balance of power and heat. According to Congdon, there is a general rule of thumb that for every 1 percent increase in frequency, you get a 3 percent increase in power usage and about a .66 percent increase in performance. As an example, if you have a processor running at 3 GHz and you increase its frequency by 15 percent to 3.45 GHz, then you are also going to increase the power usage by 45 percent and get a performance boost of only about 9 percent. At a nearly 50 percent increase in power usage, you get less than 10 percent better performance.



Going the other way, you can decrease the power usage by slowing down the processor. For example, if you decrease the frequency of a 3 GHz machine by 15 percent to 2.55 GHz, then you decrease the power usage by 45 percent at a cost of only 10 percent of your performance. In other words, you can cut the power usage by almost half and still run at 90 percent performance.

If you add additional cores to the mix, then you have the ability to reduce the power usage and still gain overall performance. Compare a dual-core system running at 2.55 GHz with the 3 GHz single-core machine. Again, the dual core is at a frequency of 15 percent less than the single-core system. With a dual-core machine, running at a 2.55 GHz frequency, your power level would be about half (55 percent) for each core when compared to a single 3.0 GHz processor. When the two 2.55 GHz cores are combined, the power consumption is nearly equal to that of the 3 GHz machine. Your overall performance, however, could be at 90 percent for each core, or up to 180 percent of the performance of the 3 GHz machine, if you can utilize both cores. The end result is a slightly slower frequency, but much greater performance at a power level that is nearly equal.

Now take this comparison even a step further by using a quad-core processor. If you reduce the frequency by 30 percent (going from 3.0 to 2.1 GHz), then you end up with power usage that is still less than half of that used by the 3.0 GHz processor (90 percent reduction for each core would be 10 percent usage for each; thus, you'd get 40 percent less for all four cores). The overall performance would end up being 80 percent for each core, which is up to 320 percent when you compare it to the original 3.0 GHz machine, if all four cores are working to capacity.

Power usage is related to heat generation. As you can see by these numbers you can drop the speed a little bit and gain big reductions in power usage and reduced heat. By using this added power to drive additional cores, you can increase overall performance to make up for the lower frequency.



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