Power, In Depth: Eight and Six Cores at 3.5 GHz
We begin with core voltage again, which climbs to an average of 1.066 V compared to the stock frequency. That's the motherboard's automatic response to elevated demands; we didn’t manually adjust the firmware's voltage setting.
Power Draw
We again compare the values from the VRM sensor to those measured in parallel at the motherboard input, calculating the losses.
An idle measurement of 18 W (that's 22 W, counting losses) and load reading of 108 W (or 121 W with losses added in) at 3.5 GHz is perfectly acceptable for a processor rated at 140 W.
| Power Consumption | Average Idle | Maximum, 100% Load | Average, 100% Load |
|---|---|---|---|
| CPU 12 V In | 22 W | 141 W | 121 W |
| CPU Package | 18 W | 110 W | 108 W |
| VRM Loss | 4 W | 31 W | 13 W |
Temperatures
Naturally, our thermal readings are low at idle. Under load, they look like this:
Let’s take a look at the time-lapse video, too.
| Temperature T | Idle | Maximum, 100% Load | Average, 100% Load (Heated Up) |
|---|---|---|---|
| Core | 27 °C | 53 °C | 45 °C |
| Package | 29 °C | 46 °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 3.5 GHz
Since our Core i7-5930K was in California with Chris, Igor deactivated two cores on his -5960X and adjusted his maximum Turbo Boost frequency to match the second-fastest Haswell-E processor. The CPUs are practically identical apart from the somewhat smaller cache, so the results should be comparable.
Core Voltage
A 1.072 V core voltage is a bit higher than before due to the higher Turbo Boost clock rate.
Power Draw
Once again, the values from the VR sensor are compared to those measured in parallel at the motherboard input, and the losses are calculated.
A reading of 16 W (with voltage regulator losses, 20 W) at idle and 84 W (with VR losses, 94 W) under load, the six-core adaptation uses a bit less power.
| Power Consumption | Average, Idle | Maximum, 100% Load | Average, 100% Load |
|---|---|---|---|
| CPU 12 V In | 20 W | 113 W | 94 W |
| CPU Package | 16 W | 86 W | 84 W |
| VRM Loss | 4 W | 27 W | 10 W |
Temperatures
Our thermal measurements under load yield the following chart:
| Temperature T | Idle | Maximum, 100% Load | Average, 100% Load (Heated Up) |
|---|---|---|---|
| Core | 27 °C | 48 °C | 43 °C |
| Package | 28 °C | 43 °C | Row 1 - Cell 3 |
| Water (In / Out) | 24 °C / 27 °C | 31 °C | Row 2 - Cell 3 |
| VRM | 33 °C | 44 °C | Row 3 - Cell 3 |
At 3.5 GHz, both CPUs (but especially the six-core configuration) give us a good impression of an architecture we might not have expected to fare as well. Haswell-E is emerging as a solid foundation for a gaming machine that can be cooled well using air or liquid.
