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Performance and Power Consumption

When it was time to measure the platforms performance, I had to decide on the competition for a more illustrative comparison. It didn’t make sense to compare against LGA775 platform, because it would definitely lose. The quad-core Intel Core 2 Quad Q9300 CPU could overclock to impressive490MHz FSB frequency on Gigabyte Intel P45 Express based mainboards. However, even in this case its resulting frequency would only be 3675MHz, which cannot compete against 3.8GHz and especially 3.95GHz by Intel Core i7-920. As for the performance comparison at the same clock speeds, our article called New Hit from Remake King: Intel Core i7 Review has already discussed it in great detail. WE have already talked about memory subsystem performance in different modes, revealed the influence of SMT, Turbo Boost and other innovations in the new CPUs on their performance. It also doesn’t make sense to compare Gigabyte GA-EX58-UD5 and GA-EX58-Extreme with one another, because their results are absolutely identical and the difference will lie within the measuring error. So, I decided to check out the performance gain from CPU overclocking.

Our test platform featured the following configuration:

  • Mainboard: Gigabyte GA-EX58-UD5, rev. 1.0, BIOS F4;
  • CPU: Intel Core i7-920 (2.66GHz, 133MHz base frequency, 8MB L3 cache, Bloomfield, rev. C0, 1.225V Vcore);
  • Memory: 3 x 1024MB DDR3 OCZ PC3-14400 Platinum Series, OCZ3P18002GK, (1800MHz, 8-8-8-24, 1.95V);
  • Graphics card: ATI Radeon HD 4870 512MB;
  • HDD: Samsung SP2504C (250GB, SATA II, 7200RPM, 8MB, rev.A);
  • CPU cooler: Cooler Master GeminII (120-mm Protechnic Electric MGA12012HB-O25 fan, 2500RPM);
  • Thermal interface: Noctua;
  • PSU: Antec NeoPower HE 550 (550W);
  • Case: Antec Skeleton.

We used Gigabyte GA-EX58-UD5 mainboard instead of GA-EX58-Extreme simple because it was in the system already at the time. I swapped the boards forth and back, reflashed new BIOS versions, replaced CPU coolers – however, the results were identical on both of them.

I ran the tests in three modes. First, in the nominal mode. A lot of users out there do not adjust the system settings to their most optimal values at all. They simply select the default BIOS profile and that’s it. So, we didn’t change voltages, frequencies or timings. Since Turbo Boost was enabled in this case, the clock multiplier increased to 21x and this mode is marked as 133x21 in the charts. In fact, Gigabyte mainboards raise the base frequency by almost 2MHz in this case thus increasing all other frequencies as well. For example, our CPU frequency was 2.83GHz instead of the nominal 2.66GHz, while the memory frequency rose to 1079MHz instead of the nominal 1066MHz.

The second mode was overclocking without increasing the processor Vcore and it is marked as 181x21. The CPU frequency was 3.8GHz and the memory frequency was almost unchanged – 1086MHz. We couldn’t increase the memory frequency, but we set more aggressive 6-6-6-18-1T timings. We also calculated the percentage of the frequency gain compared to the nominal mode.

The third mode was further overclocking to 188MHz base frequency, i.e. to 3.95GHz CPU clock. The processor Vcore was increased to 1.3V. Again, let’s check out the frequency gain compared to overclocking the base frequency to 181MHz.

Well, here are the results:

Frankly speaking, I didn’t expect a triumph like that at all. Overclocking the processor by 43% brought us an average 25% performance increase. The performance improved by more than ¼! Another 4% frequency increase results in 3.5% performance improvement. Of course, the specific values depend on the applications. The results in Crysis were especially impressive, and we didn’t even touch the graphics card yet, only overclocked the CPU and set more aggressive memory timings!

Now let’s check out the system power consumption in all three work modes. We used Extech Power Analyzer 380803. The device is connected before the system PSU, i.e. it measures the power consumption of the entire system without the monitor. We used Fritz Chess Benchmark to load the system and recorded the maximum reading in the end of the test.

And the results are actually very interesting! Overclocking without the voltage increase raises the power consumption by 17.5% on average. It makes perfect sense to refer to an average value here, because the CPU is rarely fully idle or fully loaded. It appears that overclocking improved the processor power-efficiency and performance-per-watt, because its power consumption increased only by 17.5%, while performance got 25% higher. However, we can’t say the same about overclocking with increased core voltage, because there is a squared and not linear relationship between the voltage increase and the processor power consumption. The power consumption got about 11% higher than in the previous case, while the performance improved only by 3.5%.

So, the advantages of overclocking without increasing the CPU Vcore are evident. The performance boost is more than evident, over 25%, while additional voltage increase will only add another 3.5% and the price will be way higher power consumption, heat dissipation and noise. However, if your CPU is 100% utilized all the time, even a few additional percents will help and the noise doesn’t really matter then go all the way. It is your choice.

The obtained results should be very convincing even to dedicated overclocking antagonists. Although, there is another opinion out there, too. Namely, that “normal people” will be able to make enough money to go and buy the part they need in the time it will take poor overclockers to get to the desired speeds. You should just keep in mind a few things. For example, the official wholesale price of the top Intel Core i7-965 Extreme Edition processor is $999. And as you know, this processor works only at 3.2GHz. We, however, managed to get a 3.8GHz processor without much effort. And a slight Vcore increase will push its speed almost to 4.0GHz. There are no CPUs like that in the market today, no money can buy them. Even if they appear one day, overclockers will already be conquering new heights by that time. So, you don’t have to overclock, but why not do it, if you could really use some high speeds for work or gaming?

 
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