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The Underclocking Experiment
The Underclocking Experiment - PCSTATS
Abstract: PCstats knows overclocking. You know overclocking. This got us thinking though; what about underclocking?
Filed under: CPU / Processors Published:  Author: 
External Mfg. Website: PCSTATS Dec 23 2005   M. Dowler  
Home > Reviews > CPU / Processors > PCSTATS

Underclocked Benchmarks: SuperPI and conclusions

Super Pi Source: SuperPI

SuperPI calculates the number PI to 8 Million digits in this raw number crunching benchmark. The program allows the user to change the number of digits of PI that can be calculated from 16 thousand to 32 million. Our benchmark is set to 8 Million digits and 22 iterations. The benchmark is measured in seconds; lower results are better.

8 Million Digits:


2.4GHz 394
2.3GHz 411
2.2GHz 424
2.1GHz 443
2.0GHz 459
1.9GHz 482
1.8GHz 502
1.7GHz 530
1.6GHz 556
1.5GHz 592
1.4GHz 626
1.3GHz 674
1.2GHz 721
1.1GHz 786
1.0GHz 866
900MHz 965
800MHz 1069

Now that's a smooth graph! Looking at these benchmark results, it becomes obvious how processor performance plunges as the clock speed drops. The 800MHz test wound up almost three times slower than the stock speed test, which makes sense since it was running at exactly a third of the speed.

Conclusions to this Underclocking Experiment

One thing that emerged as a definite trait of the underclocked system was predictable performance. As processor speed was reduced, performance dropped off in a predictable curve. The fact that processor-intensive applications like SuperPI suffered more than the gaming benchmarks in our tests makes sense, since the video card we used was not being underclocked in any way and was still shouldering some of the burden of the 3D benchmarks. When the video card was taken out of the equation, the performance drop was essentially equivalent to the level of underclocking.

As processor speed dropped below 1GHz, the law of diminishing returns kicked in and the decreases in performance at each speed downstep became larger. On all the benchmarks, the curve becomes more pronounced at the lower speeds, indicating that underclocking further would most likely drop performance to unacceptable levels.

If we take the numbers literally, underclocking an Athlon 64 4000+ to a third of its original speed will result in a ~7 degree drop in temperature under load, a 30-50% drop in performance in video card assisted 3D applications and a 66% drop in processor performance. On the bright side, the system would still be quite usable as a standard Internet/word processing/general work computer.

So could you repeat this experiment at home? Certainly, and you don't need to use the same equipment seen here either. The Scythe NCU-2000 is only one of several brands of passive heatsink available, and you can also use an active heatsink with an alternate fan if you want a quieter system. Remember that case ventilation is essential if you are trying to create an all-passively cooled PC though.

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< Previous Page © 2022 PCSTATS.com CPU / Processors Reviews...»


Contents of Article: PCSTATS
 Pg 1.  The Underclocking Experiment
 Pg 2.  Procedure, temperatures and voltages
 Pg 3.  Underclocked Benchmarks: 3DMark 2001SE, 3DMark2005
 Pg 4.  — Underclocked Benchmarks: SuperPI and conclusions

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