Before we dive in, we need to get the disappointment out of the way. We're going to be using a Core i7-6700K CPU to test the Z270 Gaming Pro Carbon's overclocking prowess. Unfortunately, the stars didn't align to get me a Kaby Lake sample for testing. The process of overclocking Skylake on the board will hopefully be representative of what you'd see with Kaby Lake. If you're interested in how Intel's seventh-generation Core chips overclock, be sure to check out our full review.
It's worth mentioning that a given CPU's frequency potential (also known as the silicon lottery) and your choice of CPU cooler tend to have a greater impact on overclocking results than your choice of motherboard does these days. Still, you want to get to the peak clock speed of your chip with a smile on your face rather than a grimace. The quality of the overclocking experience is where your choice of motherboard becomes important. Ideally, you want a motherboard that will help you along the way, not one that forces you to become too acquainted with your clear-CMOS jumper.
To find out what kind of travel companion MSI's Z270 Gaming Pro Carbon will be on this journey, we turned to our trusty Cooler Master Nepton 240M. The Nepton has a 240-mm radiator, and before it was superseded by the company's MasterLiquid Pro 240, it had a $110 asking price. This puts it towards the high end of the range of coolers that might be seen in a system built around the Pro Carbon. That said, it should do a good job of keeping our four Skylake cores from feeling the heat as we push the clock speeds up.
The first stop on our overclocking journey was MSI's Gaming App. After enabling OC Mode, we were asked to restart the system. Prior to the appearance of the firmware splash screen, we were notified that Game Boost was enabled and that it wasn't recommended to do any modifications under the BIOS OC Menu. The system also warned us against updating the BIOS or clearing the CMOS. So noted.
Upon booting back into Windows, we were greeted with a 4.4 GHz clock speed. All Turbo multipliers were set to 44x with the base clock at its default 100MHz. To support these speeds, the CPU was being fed 1.326V. OC Mode also set our memory speeds to 2400 MHz. With these settings, Prime95 was completely stable, no throttling occurred, and CPU temperatures peaked at 86ºC. While running Prime95 with these settings the test system drew 200W from the wall.
Next, we enabled MSI's Game Boost setting directly. This feature can be enabled either via the Command Center utility or via the firmware. Enabling it in either place results in a restart before the changes take effect.
Unsurprisingly, enabling Game Boost this way gave us the exact same 4.4 GHz clock speed and 1.326V core voltage that the Gaming App's OC Mode bestowed. As expected, history repeated itself and Prime95 was stable.
With our short list of auto-overclocking options exhausted, it was time to turn off the autopilot and see what we could do with manual tuning. We started out, as we usually do, by tweaking the multiplier alone. We left all of the voltages at their "auto" defaults. This got us to 4.5 GHz using a 45x multiplier alongside the standard 100MHz base clock. At this speed, the firmware was supplying our CPU with 1.336V. This config proved to be stable during the Prime95 run. We saw no signs of throttling, and temperatures topped out at 88° C with the test system pulling 205W from the wall while running Prime95.
We didn't get very far when we pushed the core multiplier to 46x with voltages on "auto," though. Thermal throttling reared its ugly head with Prime95 causing core temperatures to spike up to 100°C. The firmware had bumped the core voltage up to 1.408V, and our Nepton couldn't dissipate the heat. Before throttling kicked in, our test system was drawing 240W.
It was time to take voltage control into our own hands. By manually setting the core voltage, we made it to 4.6 GHz at 1.34V. Prime95 was completely stable with no throttling, and our Nepton was managing to keep temperatures in check at or below 94° C. Under these condition the test system drew 220W from the wall.
Unfortunately, 4.7GHz was out of our reach. Either Prime95 would find errors on one or more worker threads, or we'd push voltage so high that we'd hit thermal throttling.
A 4.6GHz final clock speed is very respectable for this CPU and cooler combination. It is, in fact, only 100MHz lower than the highest speed we've ever achieved on any of the Z170 boards we tested, so those numbers are right where we'd expect to be for our multiplier overclocking results.
The fun doesn't end there, though. Skylake K-series CPUs running in Z270-based boards still allow tweaking of the base clock without having to run other system devices out of spec. This change was seen originally with the Z170 chipset, thanks to a revised reference clock architecture that decouples the PCIe and DMI bus speeds from the base clock. While it's much easier to overclock using multipliers alone, we ran a quick test to see how the Pro Carbon fared when overclocking with base clock tuning.
We first tried 200MHz in the firmware, leaving everything else on "auto." The system booted perfectly, and our CPU was stable at 4.2GHz. When we tried for 250MHz, the firmware mysteriously decided that a core multiplier of 8x was in order. Bumping this to 16x got us an even 4GHz, and a stable system:
A 266MHz base clock was out of the question. The firmware elbowed in and loaded safe defaults after one failed boot attempt to let us know we had pushed too far.
Despite the Pro Carbon's fairly limited auto-overclocking functionality, this board could suit seasoned tweakers who know their way around the firmware as well as newbies who are just starting out. The pre-baked CPU overclocking profile of Game Boost was quick, easy, and stable, and the firmware's "auto" voltage settings gave us a config that only left 100MHz on the table compared to tweaking settings manually. Overall, turning the screws on our Core i7-6700K was smooth and easy.
Now that our overclocking journey has come to an end, let's see how the Z270 Gaming Pro Carbon looks from a performance perspective.
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