High performance is only one advantage of the new processors with Sandy Bridge microarchitecture. When we discussed its peculiarities, we stressed that most of its improvements are aimed not only at increasing the performance, but also at lowering the power draw. So, the new Core i5 CPUs should be more energy-efficient than their predecessors, and consequently, should exceed them substantially in terms of performance-per-watt.
You don’t have to look far for proof of that statement: just check out the TDP rates. The Core i5-2500, Core i5-2400, and Core i5-2300 processors we discuss today have a TDP of 95 W, which corresponds to the TDP of quad-core Core i5 CPUs with Lynnfield core. However, TDP parameter for Sandy Bridge processors also takes into account their integrated graphics core, which gets disabled on Intel P67 based mainboards. As a result, Sandy Bridge processors should be highly energy-efficient even in terms of calculated parameters.
Of course, we also performed some tests. The graphs below show the full power draw of the computer (without the monitor) measured after the power supply. It is the total of the power consumption of all the system components. The PSU's efficiency is not taken into account. The CPUs are loaded by running the 64-bit LinX 0.6.4 utility. We enabled all the power-saving technologies for a correct measurement of the computer's power draw in idle mode: C1E, AMD Cool'n'Quiet and Enhanced Intel SpeedStep.
Core i5 processors with Sandy Bridge microarchitecture start showing their ultimate energy-efficiency already in idle mode. In wait state LGA1155 systems consume less power than any other contemporary platforms. The new system agent in charge of advanced power management makes sure that in idle mode the frequency of Sandy Bridge processors drops to 1.6 GHz and their core voltage – to approximately 0.8 V. moreover, the idle CPU units also get disabled.
The situation looks just as good during intense operational load. As we see, the peak power consumption of a complete system with a new Core i5 processor, mainboard, memory and graphics card is around 100 W. I believe no comments are necessary at this point: the numbers speak for themselves.
When it comes to the power consumption of a processor alone, as opposed to the power consumption of the entire system, it will be interesting to check out the readings off the Sandy Bridge system agent, which constantly monitors CPU power consumption for Turbo Boost technology.
It turns out that Core i5-2500, Core i5-2400 and Core i5-2300 processors (without the graphics core) fit into a 95 W thermal envelope and still have substantial reserves left. Therefore, we were not surprised to see the new boxed cooler bundled with them:
This work of engineering art is only 20 mm tall and come with a copper center, so it should be efficient enough. Of course, I doubt to you will be able to set any overclocking records using this cooling solution, but it has another important advantage: it will easily fit into any miniature low-profile system case. And we have no doubts that Sandy Bridge processors will be a popular choice for HTPC or some other similar Mini-ITX systems. Their low heat dissipation, good performance and built-in graphics core will definitely guarantee that.