If you’re serious about squeezing the most performance out of Intel's Z68 Express platform, you need a K-series processor. These parts allow you nearly unfettered access to the clock multiplier (up to 57x) without touching the severely-limited 100 MHz BCLK. The K-series SKUs enable unlocked power/thermal specs and a range of memory bus ratios as well, letting you dial in data rates of up to DDR3-2133.
If you don’t want to spend extra money on a K-series chip and instead grab a Core i7-2600, Core i5-2500, -2400, or -2300, you still get access to what Intel calls "limited overclocking." This means you can set clock rates up to four speed bins above the highest Turbo Boost frequency.
|Maximum Overclocked Speed (all cores active)||Price|
|Core i5-2500K||5.7 GHz (unlocked 57x multiplier)||$224.99|
|Core i5-2500||3.8 GHz (limited unlocked 37x multiplier)||$209.99|
|Core i7-2600K||5.7 GHz (unlocked 57x multiplier)||$314.99|
|Core i7-2600||3.9 GHz (limited unlocked 38x multiplier)||$299.99|
So, take a Core i5-2500 as an example. The chip’s base clock is 3.3 GHz. In a worst-case scenario, all four cores are active, and Turbo Boost technology is able to add one bin worth of performance, or 3.4 GHz. Limited overclocking bumps the speed up 400 MHz to 3.8 GHz. On the other hand, a Core i5-2500K allows you to hit speeds up to 5.7 GHz by fiddling with the multiplier. It’s an obvious choice for enthusiasts. The fact that there’s only a $15 spread between the unlocked and partially-unlocked version of the same chip makes the choice even easier for overclockers.
Overclocking on Z68 Express
Overclocking on Z68 is identical to P67. The only other additional benefit you get is access to the HD Graphics 2000/3000 engine's clocks. Frankly, though, gamers will add their own discrete cards and not bother with tweaking the integrated logic.
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