Power, In Depth: Eight and Six Cores at 4 GHz
Core Voltage
Overclocked to 4 GHz, our Core i7-5960X's core voltage is now 1.110 V. This time around we're optimizing it manually to minimize power consumption and temperature.
Power Draw
The following chart contrasts the VRM's measurement with our reading at the EPS connector, in addition to power losses due to the voltage regulation circuit.
A reading of 18 W at idle is identical to what we just saw at 3.5 GHz. However, the increase to 124 W under load shows that the eight-core configuration running at 4 GHz is starting to pull quite a bit more power from the wall.
Still, these figures are within reason considering the performance you get in return.
| Power Consumption | Average Idle | Maximum, 100% Load | Average, 100% Load |
|---|---|---|---|
| CPU 12 V In | 22 W | 165 W | 146 W |
| CPU Package | 18 W | 128 W | 124 W |
| VRM Loss | 4 W | 43 W | 23 W |
Temperatures
The temperatures at idle don't increase. And as clock rate goes up, the difference between each core's minimum and maximum temperature becomes more pronounced, too.
It’s time for a look at the time-lapse video.
| Temperature T | Idle | Maximum, 100% Load | Average, 100% Load (Heated Up) |
|---|---|---|---|
| Core | 27 °C | 57 °C | 48 °C |
| Package | 29 °C | 48 °C | Row 1 - Cell 3 |
| Water (In / Out) | 24 °C / 27 °C | 32 °C | Row 2 - Cell 3 |
| VRM | 34 °C | 47 °C | Row 3 - Cell 3 |
Six Cores At 4 GHz
Again, we want to try the same thing using six cores to estimate how the Core i7-5930K or -3820K might behave.
Core Voltage
Registering 1.100 V, there’s barely any difference in CPU core voltage between the six- and eight-core models.
Power Draw
Disabling two cores yields a reduction in power consumption to 17 W at idle (21 W if you count the VR) and 101 W under load. That's notably less than the eight-core configuration.
| Power Consumption | Average, Idle | Maximum, 100% Load | Average, 100% Load |
|---|---|---|---|
| CPU 12 V In | 21 W | 137 W | 115 W |
| CPU Package | 17 W | 105 W | 101 W |
| VRM Loss | 4 W | 32 W | 14 W |
Temperatures
Here are the temperatures under load:
| Temperature T | Idle | Maximum, 100% Load | Average, 100% Load (Heated Up) |
|---|---|---|---|
| Core | 27 °C | 53 °C | 46 °C |
| Package | 28 °C | 44 °C | Row 1 - Cell 3 |
| Water (In / Out) | 24 °C / 27 °C | 31 °C | Row 2 - Cell 3 |
| VRM | 34 °C | 45 °C | Row 3 - Cell 3 |
Our eight- and six-core setups increase about 20 W when we overclock to 4 GHz. It's easy to see that we're operating Haswell-E above its sweet spot. Nevertheless, you should be able to hit a stable overclock at comparable performance levels using a big heat sink. Just be sure you have a high-end cooler and a chassis with good airflow.
