Core i7-870 Overclocking And Fixing Blown P55-Based Boards
Our motherboard roundups have shown that Intel’s LGA 1156 interface brought with it a greatly needed modicum of efficiency compared to the enthusiast-oriented LGA 1366 platform. But only part of that power savings comes directly from the Lynnfield-generation CPU core, with remaining reductions found by eliminating all remaining northbridge functionality from the chipset and reducing it to a single component. Furthermore, much of the power savings that the new CPU core provides comes from slight refinements that have allowed the new processors to operate at a slightly lower voltage, a characteristic that’s typically disregarded when overclocking.
Using the same 8MB L3 cache and 45nm die process, the 37% difference in thermal design power (TDP) between Bloomfield- and Lynnfield-based processors is only realistic when both are left at their respective stock settings. Forcing both processors to identical core voltage levels for the purpose of overclocking causes the newer part to take on much of the previous part's inefficiency, a fact revealed only through extensive testing.
Thus, when some manufacturers economized the voltage regulators of “overclocking-friendly” LGA 1156 motherboards by what their engineers thought should be an acceptable level, they were shocked to learn that these parts couldn’t stand up even to our moderate overclocking tests. The results are documented in our subsequent test of $100-$150 P55-based motherboards.
A 150W board limit certainly sounds generous enough, but our testing has proven that it’s very easy to exceed that limit even at the moderate voltage levels supported by CPU air cooling. We begin today’s investigation with a power analysis, using a board known for its solid overclocking capability, before moving on to examine how the manufacturers of two previously-failed motherboards have addressed their problems.
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