Distinctly different experiences
Now that we've established the Core i7-3770K's limits with our cooling setup, it's time to get all touchy feely with a stack of Z77 motherboards: Asus' P8Z77-V, Gigabyte's Z77X-UD3H, Intel's DZ77GA-70K, and MSI's Z68A-GD65. We'll be concentrating on CPU overclocking, since we've already published an in-depth comparison of the Asus, Gigabyte, and MSI boards in addition to a quick look at the Intel one.
Let's start with the Asus board, because it's the only one that was stable at 4.9GHz. We didn't go straight there, though. First, we tapped into the board's auto-overclocking mechanism, which is activated via the OC Tuner firmware option. The board quickly overclocked itself to 4.2GHz using a 41X multiplier and a 103MHz base clock. OC Tuner didn't increase the core voltage, and the system was perfectly stable.
Next, we tried our hand at manual tuning. There are two options: firmware and software. The P8Z77-V's firmware interface is one of the best around, and it's quick to navigate for folks who are familiar with traditional BIOS layouts. The firmware automatically increases the CPU voltage as the frequency rises, a function that isn't matched by Asus' Windows tweaking software.
Since we've already spent quite a lot of time poking around Asus' firmware, we opted for the software route. Asus' Windows utilities have come a long way in the last few years, and the TurboV EVO app is excellent. The interface is easy to use and nicely matches Asus' other apps. Options abound, including an auto-overclocking mechanism for Ivy's integrated GPU. There's also a separate application with fine-grained control over the power circuitry, and it proved invaluable in getting our CPU stable at 4.9GHz.
Ivy overclocking is best confined to the CPU multiplier, so that's the approach we took in our manual sessions. The P8Z77-V ran our Core i7-3770K up to 4.4GHz before additional voltage was required to maintain stability under load. Hitting 4.8GHz called for 1.3V, and 1.35V was needed to keep the BSODs away at 4.9GHz. At that speed, we had to set the load-line calibration to "high" to prevent Z-Zip from generating errors.
The P8Z77-V actually booted into Windows with the CPU running at 5GHz, but it crashed instantly under load, and applying extra voltage didn't help. Already, the CPU was riding the edge of the throttling threshold. We even tried tweaking some of the other system voltages, to no avail.
Next up: the Gigabyte Z77X-UD3H. Again, we started with the board's auto-tuning mechanism. This one is accessible through Gigabyte's EasyTune software, which includes a couple of pre-baked settings in addition to an auto option that cranks the frequency and runs its own stability test along the way.
After rebooting and running its Windows-based stability test several times, the UD3H settled on 4.7GHz using a 45X multiplier paired with a 104MHz base clock. CPU-Z reported a CPU voltage of just 1.248V. The system almost made it through our stress test, but when the rthdribl window was closed after a five-minute load, the system promptly crashed. Upon rebooting, the machine scaled itself back to 4.4GHz (43x103MHz) at the same voltage. This configuration survived our torture test without fussing.
Gigabyte evidently needs a better stress test for its auto-tuning mechanism. Falling back to a slower speed is a nice recovery, but the auto-tune scheme should produce a stable result the first time around. Auto-tuning mechanisms are best for newbies looking for a trouble-free overclock and seasoned enthusiasts seeking a stable starting point for their own manual tuning.
Speaking of manual tuning, we bounced between Gigabyte's software and firmware before favoring the latter. The EasyTune software messed with the temperature readings we were getting from AIDA64, and the app feels like it hasn't been updated in ages. Gigabyte does have a new power tuning utility for Windows, but it's a separate app that's much clumsier than EasyTune. Fortunately, the motherboard's new firmware interface is a real treat to use.
Mouse-friendly sliders permeate the "3D" interface, and there's an "advanced" layout if you prefer the comfort of an old-school BIOS. Like the Asus board, the Gigabyte automatically increases the CPU voltage so long as the multiplier is tweaked via the firmware. You'll need to add voltage manually when overclocking with EasyTune.
4.4GHz once again proved to be the CPU's limit at stock voltage. However, we couldn't get 4.9GHz stable no matter how much juice was pumped through the processor. Windows wouldn't load until the CPU was given 1.35V, but that wasn't enough to stave off the BSODs under load. Adding voltage only resulted in throttling and program errors. Adjusting the load-line calibration didn't make the system more stable, and neither did tweaking other power settings and system voltages.
In the end, the fastest stable configuration was 4.8GHz on 1.35V. The board was happy booting Windows and running our stress test on 1.325V, but 7-Zip errors persisted until we applied more voltage.
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