UPDATED: Overclocking Up To 3.80 GHz
The overclocking potential of the Core i7 is similar to that of the Core 2, which is to say, very good. We were able to overclock our Core i7 965 Extreme from 3.20 GHz to 3.60 GHz without raising the core voltage or encountering stability issues.
According to Intel, the Extreme Edition will continue to come with an unlocked multiplier. However, our Intel DX58SO motherboard did not allow us to increase the multiplier beyond the default value of 24 for the Core i7 965 Extreme, so we ended up overclocking by increasing the internal front side bus from 133 to 150 MHz. We set the memory multiplier to 8x, resulting in a CPU clock speed of 3.60 GHz and a memory speed of DDR3-1200.
Our US lab is able to confirm that the Core i7 965 Extreme’s multiplier cannot be increased using Intel’s DX58SO motherboard—it’s capped at 24x and can only be reduced. The only way to overclock this motherboard/processor combination is to enable Turbo Mode, increase the maximum amp/watt limits to an impossibly high number, and configure the maximum Turbo multiplier range for 1, 2, 3, and 4 core operation to your desired overclock setting. In this way, Turbo mode will never hit the maximum thresholds you define and, ideally, never throttle back. We’ll get into Turbo mode more on the next page.
The ASUS Rampage II Extreme board is able to manually adjust multiplier setting upward, however, making a 3.7+ GHz overclock as easy as keying in a 28x setting on that platform. After more extensive testing, our i7 965 Extreme peaked at just over 4 GHz, and our i7 920 sample ran stably at 3.8 GHz using the ASUS board and a mix of multiplier/Bclk/voltage tweaking.
We were only able to push our Core i7 965 Extreme to a stable 3.84 GHz by increasing the core voltage to 1.4125 Volts. Again, this was achieved by increasing the FSB to 160 MHz, giving us a memory frequency of DDR3-1280; we were unable to get our test sample of the Core i7 to run any faster. In our experience, the final retail versions of processors that show up in stores offer much better overclocking potential than the early engineering samples we get for our launch reviews. For our overclocking experiments, we set the Overspeed Protection features to 300 amperes and 300 watts.
Multipliers of the Core i7 Models
| Model | Multiplier | FSB |
|---|---|---|
| Core i7 965 Extreme | x24 | 133 MHz |
| Core i7 940 | x22 | 133 MHz |
| Core i7 920 | x20 | 133 MHz |
DDR3 Memory Required for the Core i7 920 and 940
| Frequency | FSB | 6 | 8 |
|---|---|---|---|
| 4.00 GHz | 200 | DDR3-1200 | DDR3-1600 |
| 3.80 GHz | 190 | DDR3-1140 | DDR3-1520 |
| 3.60 GHz | 180 | DDR3-1080 | DDR3-1440 |
| 3.40 GHz | 170 | DDR3-1020 | DDR3-1360 |
| 3.20 GHz | 160 | DDR3-960 | DDR3-1280 |
| 3.00 GHz | 150 | DDR3-900 | DDR3-1200 |
| 2.80 GHz | 140 | DDR3-840 | DDR3-1120 |
| 2.66 GHz | 133 | DDR3-798 | DDR3-1064 |
| Frequency | FSB | 6 | 8 |
|---|---|---|---|
| 4.40 GHz | 200 | DDR3-1200 | DDR3-1600 |
| 4.18 GHz | 190 | DDR3-1140 | DDR3-1520 |
| 3.96 GHz | 180 | DDR3-1080 | DDR3-1440 |
| 3.74 GHz | 170 | DDR3-1020 | DDR3-1360 |
| 3.52 GHz | 160 | DDR3-960 | DDR3-1280 |
| 3.30 GHz | 150 | DDR3-900 | DDR3-1200 |
| 3.08 GHz | 140 | DDR3-840 | DDR3-1120 |
| 2.93 GHz | 133 | DDR3-798 | DDR3-1064 |
