|Intel Core-i3/i5/i7 LGA1156 Overclocking Guide|
|Articles - Featured Guides|
|Written by Servando Silva|
|Tuesday, 24 August 2010|
Page 7 of 10
Overclocking Frequency vs. VoltageFor all you readers who decided to jump the first pages and go straight to the results, I must repeat that there's no interest on testing performance's difference between non overclocked and overclocked setups. That point has been addressed in all our CPU/Motherboard/RAM reviews we've done in the past, and it's up to you to decide whether you need to overclock or not, and how much is "enough" for you. Getting to the point, in this first section I'll be showing how CPU frequency increases against CPU vCore. All those charts are the result of several hours trying and testing different settings and the results reported were 100% stable (considering the stability's paradigm explained before). Not only this chart is very important for the next pages, but actually, the results in MHz shown in the next chart reveal CPU frequency used in the next pages with same voltages. So, if I reached 3700MHz with 1.2v, that means I'll use 1.2v and 3700MHz for temperature and power consumption tests too. Now that it's been clarified, let's analyze our overclocking results:
In the chart, I decided to put Stock frequencies and label them as "No OC" voltage. Actually, the second category is stock voltage (still), but this time I'm overclocking those CPUs to find what they can reach without increasing vCore. This might be the more interesting achievement for those who are looking for a balanced overclock, and by balanced I mean little extra power consumption and almost the same temperatures compared to stock frequencies, while gaining many extra MHz. CPU's architecture allows them to increase their frequency by a lot of MHz before reaching their limit within stock voltage. That's done because Intel needs to make sure every processor will work within a good range of conditions no matter how bad they are, and that also lets them sell different versions (Core i5 650, Core i5 660, etc) with same voltage values and TDP. It's all about locking CPU multiplier to the speed they want to sell and it's done. That's why high-frequency CPUs like the Core i5 680 have less possibilities to overclock the same percentage compared to its little brothers.
Going back on to the chart, the Core i3 530 was able to reach 3950MHz before starting not being stable. That's 1 GHz OC (36%) with stock voltage, and the reason I say stock voltage overclocking is the most interesting and efficient setup. The Core i5 655K however, reached 4050MHz, which is great, but overall OC percentage would be 26%. Anyway, I can't tell how many people would love to have their CPUs at 4GHz with stock voltage. Some years ago, it was too sweet to be true. Finally, the Core i7 860 reached 3700MHz for an overall 32% OC. Considering this is a nice Quad Core CPU, I think the result is more than respectable. It actually overclocked more than the Core i5 655K (overall percentage).
Next step was to add 100 milli-Volts to the CPU vCore in order to see what we could reach with 1.30 volts. At this voltage, CPU is cold enough to be cooled by Intel's stock cooler and power consumption doesn't increases a lot yet. The Core i3 CPU sample achieved 4250MHz while the Core i5 655K achieved 4.3GHz. Both of these CPUs still remained below 55 degrees at full load, which is very nice. The Core i7 860 reached 3950MHz but the temperatures increased along with power consumption. I'll explain all those other measured variables in the next pages.
Finally, I set vCore to 1.4v and overclocked until I reached 4400MHz with the Core i3 530, 4500MHz with the Core i5 655K, and a very nice 4250MHz frequency for the Core i7 860. This would be the maximum voltage I'd ever suggest to use for a 24/7 overclock. However, I added some extra voltage to reach 1.5v and see if it was worth the time. I've included 1.5v results in the next pages just to demonstrate how bad would this setting be for a 24/7 overclock, even both Core i3 and Core i5 processors still managed to squeeze 200-300 extra MHz with this voltage. I didn't have to increase QPI/VTT Voltage for the tests as my motherboard scales very well at these ranges. However, it might be different in your setup depending on many variables like RAM, ambient temperatures, airflow and number of installed devices.