Closer Look at Core i5-2400S
The introduction of Sandy Bridge processors with an “S” suffix in their model name is no big news. Processor modifications with lower power consumption that had an “S” in their model name have been out there before. However, bow this CPU series finally has processors with an integrated graphics core, which makes them even more suitable for compact systems. Especially, since the declared 65 W TDP refers to both: the computational and the graphics core together. And if we take into account that the TDP of Intel H67 Express chipset required for the integrated graphics core to work is only 6.1 W, we can easily picture a fully-functional system built around a modern high-performance quad-core processor, which will only need a 100 W power supply.
It is extremely important that Intel decided not to raise the prices on their energy-efficient Sandy Bridge models: they are only $11 more expensive than their 95 W analogues. Although you shouldn’t forget that S-processors are also a little slower.
In fact, low price of the energy-efficient CPU models comes from the way they are manufactured. Intel doesn’t sort out better semiconductor processor dies, but simply lowers the processor core voltage and clock frequency. For example, the nominal clock speed for Core i5-2400S is 2.5 GHz, while Core i5-2400 works at 3.1 GHz default frequency.
20% lower clock frequency allowed Intel to reduce the CPU Vcore to 1.05 V for our Core i5-2400S model. Other than that our energy-efficient model and the regular processor with 95 W TDP have identical specifications.
Note that despite significantly different nominal clock rate, Core i5-2400S almost catches up with Core i5-2400 in Turbo mode. In other words, Turbo Boost technology is much more aggressive by the energy-efficient CPU, so it can boost its clock speed quite seriously when not all processor cores are utilized.
Here we see a very interesting picture. When all four cores are loaded with work, our energy-efficient Core i5-2400S will fall far behind his 95 W brother. However, if only one or two processor cores are utilized, Core i5-2400S will perform very close to the regular Core i5-2400 due to Turbo Boost kicking in. it is much more interesting to compare Core i5-2400S against Core i5-2300: it is absolutely impossible to tell which CPU is faster, as it will all depend on the type of operational load at a given moment of time.
In order to illustrate what it looks like in reality, we tested processors in Fritz chess benchmark, which can generate random number of threads to perform calculations.
If we compare the performance of an S-processor against regular LGA1155 CPU models, we will immediately notice a drastic change that happens when we have two or more threads in place. When only one or two cores are working, Core i5-2400S looks quite strong, but when we get to more computationally heavy tasks, it yields even to Core i5-2300. Deteriorated multi-core performance is the ultimate price you pay for lower power consumption and heat dissipation.