Which cpu would be better, an i5-3570k with an Asus P8Z77-V LK or an i5-4670k with a Gigabyte GA-Z87-D3HP for twenty dollars more? Thank you.
Our first-hand information involves a high double-digit number of processors, including samples and final shipping boxed CPUs. Sort testing was limited to 1.2 V to keep heat manageable. Ring/cache ratios are pegged at 3.9 GHz, with the memory controller operating at 1,333 MT/s. Of the chips available for sorting, only one is stable at 4.6 GHz under full load. A few are capable of operating at 4.5 GHz. More run stably at 4.4 GHz. Most are solid at 4.3 GHz and down. As you stretch above a 1,600 MT/s memory data rate or a ring ratio to match your highest single-core Turbo Boost ratio (which helps maximize performance), your top stable core frequency tends to drop.
The first thing you need to know about Haswell you already found out in our review (read it here if you haven’t already) – it runs hot. You will need a lot more than the stock cooler if you want to overclock. With a very good air cooler or all-in-one water cooler, you’re looking at a heat limited voltage cap of about 1.25 V. At that voltage with air or AIO cooling, you’ll be seeing temperatures in the upper 80′s to lower 90′s (°C) range under normal full processor load.
Asus has tested hundreds of Haswell CPUs as part of its effort to profile the chip for auto-tuning algorithms. According to the motherboard maker, Intel's new hotness has a little less overclocking headroom than Ivy Bridge does. Perhaps more importantly, Haswell apparently has more variance from chip to chip, especially in the voltages necessary to hit specific speeds.