Power And Temperature In Detail
Idle Power Consumption
If our measurements and the sensors are to be believed, then the two CPUs’ power consumption at idle is well under 5W without integrated graphics. Running with integrated graphics enabled and without an external graphics card results in less than 6W. Desktop graphics that only consume 1W are unheard of. Whether you're talking about previous-gen Intel or current AMD solutions, every other implementation uses a lot more power.
Gaming Power Consumption
Let’s think back to our GTA V performance test. We’re rendering a power-hungry scene (driving a car at night) using the integrated recorder to create a load for our measurements. The average power consumption of Intel's Core i5-5675C comes in at a moderate 42W, whereas the Core i7-5775C consumes 52W. The peaks show that these numbers might go up if the CPU is maxed out. We’ll take a closer look at this soon with our stress test.
So what happens when the integrated graphics engine takes over rendering duties? This limits the processor's x86 cores, and its peaks are consequently not as pronounced as they were (starting toward the middle of our test run). The power consumption of the two CPUs becomes almost identical in this scenario, which makes sense, since the Iris Pro implementations are identical. The power consumption averages approximately 62W.
Maximum Power Consumption (Stress Test)
We’re putting the whole processor under maximum load to see how the picture changes. Both Broadwell-based models are plotted in separate graphs to make them easier to see. These charts show the telemetry’s frantic efforts to adjust the load nicely. This is similar to what we’re used to seeing from today’s graphics cards.
The more mainstream Core i5-5675C comes in at 65W, which is just shy of its 66W TDP. Intel's Core i7-5775C is more liberal, which is to say that it consumes 74W, or approximately 10W more than its smaller sibling. The reason for this is its higher clock rate, as well as Hyper-Threading technology keeping the available cores better-utilized. That latter feature yields a significant speed-up in tasks able to exploit threading (such as our stress test), though it does affect power consumption.
We’ll get to how all of these results stack up to Intel's previous-gen architectures and AMD's competition on the next page. Before that, though, we need to cover the by-product of power consumption: heat.
Temperatures at Full Load (During the Stress Test)
All parts of the processor (including the integrated graphics) need to be stressed to generate a significant amount of waste heat. The average temperature across all cores after 30 minutes is 52 degrees Celsius for the Core i5-5675C and 58 degrees Celsius for the Core i7-5775C. The package temperatures are a maximum of 40 and 43 degrees Celsius, respectively. We’re cooling the processors on our usual benchmark system with a Raijintek Triton 360 All-In-One open-loop compact liquid CPU cooler.
It’s hard to compare these temperatures to those generated by discrete graphics cards, since the new architecture's power consumption is significantly lower. If the performance-to-power consumption ratio is taken into account, then Broadwell stays significantly cooler.