Overclocking limit due to motherboard?

Having just watched Logan's Asus P8Z77-I review, I'm wondering what effect motherboard power supply design can have on overclocking.

Currently I have a mini ITX system with a 3570k running at 4.5GHz on a Asrock Z77E-ITX.


It has a 6+2 "digi power design". Two less than the Asus

I've been running 4.5GHz without any problems on offset mode (voltage maxes out at 1.288V) using a corsair H60. Can't seem to go any higher though. 4.6GHz works with a bit more voltage but will occasionally go unstable when CPU loads change. The only way I can seem to get higher speeds is to used Fixed voltage mode rather than offset voltage mode (this makes the processor always run hot). I suspect this may be due to vdroop or something related to voltage transient when load changes? I've never gone above the 1.3V mark when it comes to overclocking because it just doesn't give me enough return in speed. I've hence seem to have hit a wall at 4.5GHz

I don't have much headroom in the temps. In a ~21degC room, my temps max out at 85degC and idle at 33degC. I delidded my CPU a few weeks ago to replace the internal TIM with arctic silver ceramique. Worked great, dropped max temps by near 10degC!

So back to my question.. Why the massive daughter board? Does it really help?

Short answer, yes. For overclocking, you need a great VRM for ideal stability. Something like an Asus Rampage IV Extreme is going to have a 12 phase power phase, where your Asrock has a 6 phase. The RIVE is a crazy board, and takes 3930ks up past 5.0gHz regularly, at reasonable if not great voltages (very much dependant on your chip), where your Asrock would require more voltage for equal stability. The higher-end OCing boards, such as the Asus ROG series, have an additional 4-pin CPU (EPS) power for additional stability at crazy OCs; basically, you can deliver 1.5 times as much power as with a standard 8-pin motherboard. You are fine with a 6+2, but ideally, you would want an 8+2, 8+4, 12+4, 12+6, etc.