Overclocking is a sort of rite of passage for PC enthusiasts. You’re not truly hardcore until you’ve pushed your hardware beyond the stock speeds defined by the manufacturer. Back in the day, that meant fiddling with DIP switches, navigating arcane BIOS interfaces, and sometimes even making hardware modifications with a #2 pencil. Also, we had to walk barefoot through several feet of snow just to get our hands on the hardware; Newegg wasn’t around, and Amazon only sold books.

Today, clock boosting couldn’t be easier. AMD and Intel both offer CPUs with fully unlocked multipliers, the holy grail of overclocking. Pushing one’s CPU past its default speed requires little more than turning up the multiplier. That can be done through increasingly user-friendly firmware interfaces and Windows software. Some boards will even overclock themselves—with and without your permission.

The obvious question, of course, is how Ivy Bridge fits into the overclocking picture. Intel’s Sandy Bridge CPUs have offered a decent amount of clock speed headroom since their debut early last year, and all eyes are on Ivy to see if she can replicate that feat. To find out what the new platform has to offer overclockers, we’ve spend some quality time pushing the new Core i7-3770K on Z77 motherboards from Asus, Gigabyte, Intel, and MSI. Read on to see what we’ve learned.

Free as in headroom

There are all kinds of overclockers in the enthusiast community. Some spend ridiculous amounts of time—and money—on elaborate contraptions that chill CPUs using liquid nitrogen. Others plumb their PCs with intricate networks of water-cooling tubing. Those camps tend to seek out the absolute limits of their CPUs. However, most enthusiasts seem content to tap the “free” clock speed headroom that can be exploited with affordable air cooling. Rather than probing the extremes, we’re going to see how far the Core i7-3770K goes with the sort of air tower one might expect to find inside the average enthusiast’s PC.

After rummaging through the collection of heatsinks that has accumulated in the Benchmarking Sweatshop, we settled on a Thermaltake Frio. This is the same cooler we use on our storage test systems, and at $48 online, it’s eminently affordable. The radiator is lined with more fins than we’d care to count, plus five heatpipes and dual 120-mm fans.

Where’s the second spinner? It interfered with the taller heatspreaders on our Corsair Vengeance DIMMs, so the Frio had to make do with just a single fan for much of our testing. The clearance issue affected all four of the Z77 boards in our labs. We also had trouble getting a couple of larger Noctua coolers to fit, so the problem isn’t unique to the Frio. Most motherboards put their DIMM slots too close to the socket to allow massive air coolers to coexist peacefully with taller memory modules.

As it turns out, the second fan didn’t end up making much of a difference. When we switched to a dual-fan setup with a pair of low-profile Kingston DIMMs, we didn’t notice a substantial decrease in CPU temperatures. The second fan didn’t help the CPU hit higher speeds, either.

That’s not to say that our overclocking endeavors weren’t limited by our system’s cooling setup. Although we managed to get up to 5GHz on a couple of the boards, the CPU temperature climbed high enough to boil water. Thermal throttling was rampant, forcing us to back off to 4.9GHz, the highest speed our Core i7-3770K would sustain under load.

To hit 4.9GHz, we used a 49X multiplier with Ivy’s stock 100MHz base clock. It’s also possible to increase the CPU frequency by turning up the base clock speed, but since that clock affects other system components, it’s best to stick to multiplier tweaking. We were never able to squeeze more than a few MHz out of Sandy Bridge’s base clock, and Intel says Ivy has a similar range.

Our Core i7-3770K needed 1.35V (which CPU-Z detected as 1.368V) to remain stable at 4.9GHz. The system was stressed with AIDA64’s built-in torture test running alongside the rthdribl HDR lighting demo. That tandem made for a good quick test, but 7-Zip proved to be the final arbiter. When we ran it to gather final performance numbers for each motherboard, the app spit out errors with configurations that were previously thought to be stable.

I was a little surprised to hit obvious thermal limits with the chip running at such a relatively low core voltage. Then I looked at the power consumption. Here are some wattage numbers for the entire system, sans monitor, taken from the wall socket. A multi-core Cinebench render was used to generate the load.

Yeah, that’s a pretty big difference under load. 4.4GHz represents the highest speed we achieved at the default voltage, which CPU-Z reported as 1.128V. That 500MHz jump over the Core i7-3770K’s 3.9GHz peak Turbo frequency consumed an additional 17W at the wall socket. Going up another 400MHz with a voltage bump of 0.24V sent the reading on our watt meter up by nearly 100W.

Processor power consumption is proportional to the product of frequency and the square of the voltage, so increasing the latter can really cause the wattage to rise. We crunched the numbers, and our results fit the formula nicely. Serious cooling will be required to push Ivy to its limits. At the same time, taking Ivy up to around 4.4GHz should require only modest cooling, provided the CPU voltage is untouched.

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.

Intel’s DZ77GA-70K is the only board of the bunch that doesn’t have an automatic overclocking system. We’ve actually seen auto-tuners on Intel boards prior to the Sandy Bridge generation, but the company’s recent efforts seem focused on a sort of auto/manual hybrid accessible via the firmware. The main interface offers a CPU clock speed slider that users are free to drag up to 4.5GHz. The slider increases the multiplier without touching the base clock or the voltage. It does, however, ramp up the current limit so the CPU isn’t starved for amperage.

For our pseudo-auto overclock, we dragged the slider all the way to the right and rebooted. The system returned at 4.5GHz, and it remained BSOD-free for the extent of our stress test. Hitting higher speeds would require getting our hands a little dirtier.

I really like Intel’s new motherboard firmware, and its advanced overclocking options offer plenty of multiplier headroom to hit higher speeds. The drop-down menus for the voltage settings are a little cumbersome due to the sheer number of options, though. Intel would do well to allow users to key-in voltages directly. It would be nice to see an “auto” setting that increases the CPU voltage automatically as the frequency rises, too.

Ultimately, most of our time was spent overclocking the Intel board using its Windows software. The Extreme Tuning Utility is very slick, offering just enough options along with a nice monitoring panel. There’s also an integrated stress test, although we elected to use our own.

Pushing higher than 4.5GHz at stock voltage proved impossible, but an extra 100 millivolts got the CPU to 4.7GHz without issue. 4.8GHz required another 100mV, which produced a 1.336 CPU voltage according to CPU-Z. That was enough juice to get the CPU to load Windows at up to 5GHz. However, the system crashed under load. Applying more voltage resulted in throttling, which struck again when we ran our 7-Zip and x264 tests at 4.9GHz. We had to sacrifice another 100MHz to get a rock-solid system.

Finally, we come to the MSI Z68A-GD65, which has the easiest auto-overclocking mechanism of the bunch. All the user has to do is hit the OC Genie button in the corner of the board. When the button is depressed, the board boots using an MSI-optimized overclocking profile. Users can tweak this profile themselves, but we went with MSI’s defaults for this leg of the overclocking journey.

OC Genie proved very conservative, taking the Core i7-3770K up to 4.2GHz by adjusting only its multiplier. The system endured our stress test without breaking a sweat, so we started tweaking settings manually.

MSI’s ClickBIOS II firmware is a big improvement over the company’s initial efforts, and I like the fact that it has an accompanying Windows application with an identical interface. There’s something to be said for maintaining consistency between the firmware interface and Windows utilities. Unfortunately, the Windows app takes forever to load up and apply changes. Modifying the multiplier requires a reboot, which isn’t the case for other Windows tuning apps, including MSI’s own Control Center software.

Control Center still takes longer than it should to load, but changes are applied almost instantly. Multiplier tweaking was all it took to get the Core i7-3770K up to a stable 4.5GHz. Higher frequencies required more voltage, exposing an issue with Control Center. Setting 1.2V in the app produced 1.192V in CPU-Z, but bumping up to 1.3V resulted in a reported voltage of only 1.208V. Assigning a 1.3V CPU voltage in the firmware produced 1.304V in CPU-Z, so we dropped Control Center for the remainder of our testing.

The system was stable up to 4.7GHz on 1.2V, and it hit 4.8GHz on 1.3V. Adding another 100MHz required 1.35V and seemed to be throttle-free. However, 7-Zip wouldn’t run for more than a minute without producing an error. Upping the CPU voltage didn’t help, and neither did fiddling with the other system voltages and power settings. In the end, we had to drop to 4.8GHz to banish the 7-Zip errors.

A quick look at performance

If you’ve read our review of the Core i7-3770K, you know how its performance stacks up at stock speeds. You’ve also seen how much additional performance can be gained by turning the frequency up to 4.9GHz. At that speed, Ivy Bridge nearly matches the performance of the Core i7-3960X, which is based on Sandy Bridge-E silicon that offers two more memory channels and CPU cores.

So, what about the configurations we’ve discussed in this article? 7-Zip and the x264 encoding benchmark were run on all the boards at their highest stable settings. The Asus was tested with the CPU at 4.9GHz, while the others had it clocked at 4.8GHz.

100MHz amounts to around 2% when you’re running at speeds this high, so it’s no surprise to see all the scores so close. The Asus P8Z77-V generally comes out on top thanks to its clock speed advantage. However, it has the lowest frame rate in the second pass of the x264 test.

Overclocking on the sly

For quite some time, we’ve complained that Asus’ motherboard firmware engages in overclocking behind the user’s back. If a manual memory multiplier is set, the CPU’s single-core Turbo multiplier is applied to all-core loads. The Core i7-3770K runs at 3.9GHz when all its cores are occupied instead of the default 3.7GHz. This constitutes overclocking, according to Intel, and it shouldn’t be done without the user’s consent. Even worse, it violates good practices for enthusiast firmware: modifying one setting should never change another, and especially not one that’s completely unrelated.

Asus doesn’t ask permission when applying this “multicore enhancement.” The firmware’s all-core Turbo frequency display is changed to reflect the overclocked speed, but the user isn’t given an explicit message about what’s going on. At least this feature can be disabled in the firmware; we just wish it weren’t enabled by default.

When defending this behavior, Asus has insisted that other motherboard makers engage in similar dirty tricks. We didn’t see any evidence of that when testing Z77 boards with a Sandy Bridge CPU. However, we did catch one more offender when we switched to Ivy Bridge. Gigabyte’s Z77X-UD3H plays the same game with Turbo multipliers if the memory speed is set manually. Our Core i7-3770K runs at 3.9GHz with an all-core load when the memory is set to run at 1600MHz. When the memory divider is left at “auto,” the CPU speed tops out at 3.7GHz when all cores are active.

Does the Gigabyte firmware ask permission? Nope. Indeed, nothing in the firmware even informs the user that the CPU has been overclocked. Although the status window displays a 39X multiplier for all-core loads, it does so regardless of the memory configuration—including when the board is using the correct 37X multiplier.

We haven’t had time to grill Gigabyte about this behavior, which can only be corrected by setting the CPU’s per-core multipliers manually. Ugh. It’s hard to view this trend as anything other than an underhanded attempt to inflate benchmark scores. There’s more evidence that Asus and Gigabyte are pushing boundaries, too. According to CPU-Z, the Z77X-UD3H’s default base clock speed is 100.88MHz, while the P8Z77-V is clocked at 100.52MHz. I’m not going to get too worked up over sub-MHz increases to clock speed, but it’s worth noting that MSI nails the 100MHz default exactly. The Intel board runs a smidgen slower, at 99.78MHz.