Kaby Lake G CPU Performance
As important as graphics performance is, we also want to assess the Core i7-8705G as a CPU. For that we broke out a few that we think it should compare well to, starting with the ubiquitous Core i7-7700HQ in the original Asus ROG Zephyrus laptop.
We also wanted to see how a higher-end chip would perform so we ran a few tests on a Lenovo Legion Y920 with its Core i7-7820HK in default stock mode (which was pretty conservative) and in its manual “turbo mode.” The Legion has a base default setting and an overclocked setting, which we also tested on. The last chip is the one that’s simply not fair, but it would be wrong to not include: The new 8th-gen 6-core Core i7-8750H in an MSI GS65 Stealth Thin.
One big caveat: Unlike reviews of desktop CPUs, a review of a laptop CPU isn’t just the CPU—it’s really the entire platform being judged. With a laptop you have no control over the cooling, the motherboard, or any of the other components.
Making this even more difficult is what each laptop maker decides to tune for. More noise? Less heat? More performance? Any of these can impact CPU performance greatly. Ideally, you’d want to be able to use the same platform for all of the tests, but that’s just not possible right now.
Still, that doesn’t mean comparisons are worthless. For the Core i7-7700HQ performance, for example, we made sure to do spot checks of the ROG Zephyrus against other Core i7-7700HQ results we’ve seen. For the most part, it’s right where that particular Kaby Lake CPU should be.
Cinebench R15 performance
Our first test is Cinebench R15. This 3D rendering test is almost entirely a CPU test and loves threads and clock speed.
Although the 6-core leads the way by a yuge margin, you have to respect the numbers of the Kaby Lake G Core i7-8705G as it outperforms both 7th-gen CPUs. The reason for this is simple: We’ve noticed Intel and vendors are far more comfortable pushing 8th-gen chips to higher clock speeds than the 7th generation.
The world isn’t about multi-threaded code, though, so we also run Cinebench using a single thread to simulate how the CPUs would perform in the vast majority of applications.
When measuring single-threaded performance, the number of cores no longer matters, so we see the 6-core Core i7-8750H come back down to earth. Just as we saw with multi-threaded loads, both 8th-gen CPUs have a significant clock speed advantage. The Core i7-8750H is on top, but nipping at its heels is the Core i7-8705G. Surprisingly, the Core i7-7820HK, even in its manual overclock mode, is running at lower clock speeds than the 8th-gen parts.
One weakness of Cinebench R15 is that it takes only a minute to run on fast CPUs. To see what happens to the CPU after a laptop heats up we turn to Handbrake, where we convert a 30GB 1080p file using the Android preset. This can take anywhere from a couple of hours on a dual-core CPU to 45 minutes on a quad-core CPU.
What we typically see on Core i7 CPUs is much flatter performance, once the high clock speed advantage it has burns off. While most Core i7 CPUs might run at 3.9GHz for a minute or three, they will usually perform 90 percent of the work at 3.6GHz or 3.5GHz.
The 6-core Core i7-8750H easily wins this thanks to its two additional cores. On the Core i7-8705G Kaby Lake G, we see it nearly dead-even with the Core i7-7700HQ CPU. Oddly, the performance of the Legion Y920 on default speed is pretty sedate. Push the turbo slider, though, and it’s off to the races.
It’s not just Handbrake and Cinebench that agree. We also ran the set of laptops through the Chaos Group’s V-Ray benchmark. It’s another multi-threaded benchmark that can run on the CPU or GPU. For this test, we chose the CPU test. The result again sees the 8th-gen Kaby Lake G ahead of the 7th-gen CPUs except when the Core i7-7820HK is overclocked. And yes, Core i7-8750H, you can stop showing off. We get it: 6 cores > 4 cores.
Next is VeraCrypt AES Encryption benchmark. The Core i7-7820HK finally squeaks out ahead on its default setting, but let’s just call this a tie all the way around (yes, except for you, 6-core Core i7), and a pretty good showing for a convertible laptop with Kaby Lake G inside.
Let’s cap this off with our final test, where we take Cinbench R15 and measure performance with the thread load manually set from one to eight. It’s no surprise that the Core i7-8705G is ahead under all loads over a 7th-gen Core i7-7700HQ.
One problem with the above chart is that it doesn’t actually show the percent increase, which might lead you to think the Core i7-8705G’s CPU performance edge is on the far right. The actual performance edge of the Kaby Lake G is on the far left.
TL;DR: It’s all clock speed
It’s no surprise that the 7th-gen CPUs aren’t that much different from the 8th-gen chips. What’s different is the clock speeds they run at. Intel has been using the 14nm process for so long now, it’s comfortable pushing far higher clock speeds. To get a feel for how much higher, we again took Cinebench and logged the clock speed of the CPU when it was 20 seconds into the test. This particular chart has the scaling set for readability, but you’re basically looking at a 200MHz across-the-board performance advantage.
What about thermal limitations?
You know Kaby Lake G uses Dynamic Power Sharing to help goose the CPU performance to top speeds, but you’re probably wondering how much of a limitation that is when there’s a GPU load, too. To find out, we ran the graphically intense Furmark stress test on the Spectre x360 15. We then ran Cinebench R15 and saw a pretty steep decline in its score. We don’t want to put a firm number on the performance because it never stabilized. That’s a bad thing, right?
That’s what we initially thought, until we ran the same load on an older Dell XPS 15 9560 with a Core i7-7700HQ and GeForce GTX 1050. In actual performance, both are somewhat similar when the CPU and GPU are tested alone. In a stress test of both, we actually saw the Core i7-8705G and Radeon RX Vega M GL manage its thermals far better than the Core i7-7700HQ and GeForce GTX 1050 combination. In fact, once it was heated up, the XPS 15 with traditional CPU+GPU performed far worse.
While this won’t apply to all Kaby Lake G laptops, it’s definitely a sign that we can’t assume the combined package will under-perform a traditional CPU+discrete graphics setup, because in some cases, it’s faster.
Overall, we’re pleasantly surprised by Kaby Lake G. We expected CPU performance closer to a low-wattage CPU, and GPU performance below a GTX 1050. Instead, we saw better performance than a 7th-gen Core i7 high-wattage chip, and GPU performance more on a par with a GTX 1050.
Remember, too, that the Spectre x360 15 is a 2-in-1 that converts to a tablet. We’ve seen a few 15-inch convertibles with high-power parts in them, and they generally under-perform traditional clamshell designs. With Kaby Lake G, you can apparently have your cake and still fold it back into a tablet, too.
Here’s why Nvidia (and AMD) should be scared of Kaby Lake G
As good as it is, Kaby Lake G isn’t going to shake up the CPU+GeForce scene today. But tomorrow, if there’s a Cannon Lake G or a Whiskey Lake G with more cores and better graphics, AMD and Nvidia should be worried.
What’s bad for Nvidia is how the integrated-CPU-and-GPU design concentrates power with Intel. If Intel buys the graphics chip and adds it, the laptop vendor is no longer making the choice, potentially freezing out Nvidia.
AMD isn’t sitting pretty either. Today Intel is buying Radeon graphics, but the company recently announced its intent to make its own discrete graphics. It’s entirely possible a future “G” chip will feature Intel discrete graphics, not AMD’s.
Today though, there are few takers of Kaby Lake G. In fact, only two vendors have shipped it: HP with the Spectre x360 15, and Dell with its XPS 15 2-in-1. Some we’ve spoken to have painted that as a failure of Kaby Lake G to catch on, while others have speculated politics to be the cause. Whatever the truth, it’s a shame, because applied the right way in the right laptop, Kaby Lake G is a road worth taking.