Intel Core 2 Duo E7600
While all current AMD solutions are unified for the same Socket Am3 form-factor, Intel processors are pretty diverse in this respect. At this time CPUs from this manufacturer support three independent platforms: LGA775, LGA1156 and LGA1366. We are going to start with the oldest socket type today. And the first CPU we picked for our LGA775 tests will be Core 2 Duo E7600 based on a 45 nm Wolfdale core that saw the light of day back in 2008. Processors designed in this form-factor has already moved into the low-end price segments, but they are still desired by many computer enthusiasts due to their excellent performance and overclocking potential. Unlike pilot CPU models on Wolfdale core, Core 2 Duo E7600 has slightly simpler specifications. Its clock frequency is 3.06 GHz, it supports only 266 MHz system bus and has a shared 3 MB L2 cache.
Although Core 2 Duo E7600 is manufactured with the same 45 nm process as all contemporary AMD processors, its nominal voltage is considerably lower than that of the AMD solutions. It was set at 1.275 V for our particular CPU. Moreover, it shouldn’t exceed 11.3625 V for the mass production processors of this type anyway. As we have already seen during our first tests, core voltage does affect power consumption and heat dissipation a lot, that is why it is not surprising that the TDP of our Core 2 Duo E7600 processor is only 65 W. In reality a complete system equipped with this processor consumed no more than 96 W (when the CPU was loaded to the fullest extent, but not the graphics card), and it means that Core 2 Duo E7600 is considerably more energy-efficient than Athlon II X2 255. Another great example, is the power consumption along the processor power line – during our tests in nominal mode it never exceeded 45 W.
Keeping in mind that Core 2 Duo E7600 supports only 266 MHz bus, it is fairly easy to overclock, even though Intel locks the clock frequency multipliers for all their processors except the most expensive ones. Without touching the core voltage we managed to get our CPU to work stably at 3.6 GHz, and he best result obtained in our testbed was 4.0 GHz. The table below lists all intermediate steps undertaken in order to reveal the connection between the frequency and power consumption:
All other voltages not mentioned in the table above were at their defaults.
I have to say that in this case the dependence of power consumption on the clock frequency promises to be somewhat more interesting than what we saw by AMD CPUs. Here we had to increase Vcore not only in order to conquer that last overclocking threshold, but even a little sooner than that. As a result, the flat curve on the graph and its abrupt growth should start not at the last overclocking increment, but at the one before.
And it is really so. As we see, power consumption starts increasing dramatically only when the processor core voltage increases. When we overclock with the default Vcore settings, every additional 200 MHz frequency increase produces only 2-3 W of extra power consumption. In other words, in terms of dependence of the total power consumption on the processor frequency and core voltage, LGA775 platform behaves just like Socket AM3.
However, the power consumption layout along the mainboard power lines looks completely different:
In fact, we could probably say that if we take a mainboard with a different implementation of the processor voltage regulator circuitry (for example, one from a different manufacturer), the picture will be different. Nevertheless, we notice significant currents going along 3 V power line that increases a little bit during overclocking. It seems logical to assume that this line powers the chipset North Bridge that contains the memory controller in LGA775 systems. As for the power consumption along the 12 V processor power line, it doubles during Core 2 Duo E7600 overclocking. It turns out that although this processor in its nominal mode consumes about 45 W of power under heavy load, 30% overclocking pushes its power consumption to 94 W. moreover, power consumption increases mostly at the last two increments, when in addition to raising the FSB frequency we also had to increase the CPU Vcore to ensure system stability.