With the release of the 6th Generation X1 Carbon, Lenovo created one of the best performing ultrabooks ever made. Thanks to the core bump from two to four, performance of the device nearly doubled without much compromise (up to their thermal limits, which are likely greater than you might assume, even in an ultrabook of this size). Intel bumped it up a notch yet again with the release of a single hexa-core ULV SKU in 2019, and Lenovo was gracious enough to include it in a refresh of its 7th Gen X1 Carbon, which we’ll be looking at now from the lens of a long time ThinkPad enthusiast.

Summary of Changes

With the majority of applications now supporting multi-threading of some kind, the story got even more exciting in 2019 and 2020 with the release of the 7th Gen X1 Carbon refresh — and, as of the recent announcement, the 8th Gen X1 Carbon — both of which will feature this top-tier configuration:

The i7–10710u hexa-core processor,

a 3-Cell 51Wh Battery,

a Low Power FHD Display,

Dolby Atmos 2 Tweeter +2 Subwoofer Speakers,

and 16GB of LPDDR3 RAM

We will be comparing this configuration to the 6th Gen X1 Carbon, which I reviewed for its CPU performance in the context of the entire Kaby Lake-R line, after tweaking and playing with it to squeeze every last clock cycle per watt out of it. While the 6th Gen X1 Carbon that we looked at included the WQHD display and a slightly larger battery, the model we have includes a Low Power FHD display for its battery efficiency (which is also the reason we went with the hexa-core processor). This review will be focusing mostly on the biggest change here — the hexa-core CPU, but we will touch lightly on the other changes as well before diving into the raw numbers.

Display

The latest generation of ThinkPads include another nice addition which are low power Full HD displays. These 1080p displays function identically to the screens you are used to in the past, except they consume significantly less power at every level of brightness. Traditional displays draw 40% — 100% more power compared to LPDT display found here.

While the brightness figures aren’t advertised, a “traditional” 1080p display draws an average of 2 watts. At peak brightness (400 nits), the LPDT displays draw 1.6 watts, with an advertised consumption of 1 watt on “average”. Taking the 40%–-100% figure at face value, we can assume that traditional displays draw upwards of over 3 watts at maximum brightness.

A saving of 1–2 watts seems minor, but this represents a massive savings overall when taking into account that the entire device draws 3.5W —7W under light web browsing and web tasks (compared to the 5W — 8W of the previous generation). That equates to an average additional run time of over an hour on a full battery due to the display savings alone, depending on the use case. This is definitely something to write home about, and is one of the the biggest positive changes to this generation’s machine.

Keyboard

The first generation X1 Carbon had a whopping 2.1mm of key travel. Every generation of X1 Carbon from the 2nd gen onward has had 1.8mm of key travel, a quite respectable amount for the ultrabook class of laptops. Up until the 5th Generation, this was lower than other ThinkPads, but still best in class. When the 6th generation rolled around, the 1.8mm travel of the Carbon actually became the deepest key travel of any current ThinkPad, sans P series.

Alas, all good things must come to an end. The 7th X1 Carbon reduces this key travel to 1.5mm, a 20% reduction from the 1.8mm I have become accustomed to in the previous generations. Still more than usable, and in a landscape of 0.5mm key travel keyboards (Apple, WTF?), I can hardly complain.

Many users report the newer keyboard being a more pleasant typing experience due to the keys and TrackPoint buttons now being flat. I definitely agree that the shape of the keys themselves feel better on my fingers. Unfortunately, this change was likely done not for the user experience, but to thin out the device further, and key feel aside, the shallower keystrokes do not feel as nice to actually type on when compared to previous generations.

Battery Life

Another concession made this generation was the downsizing of the battery. The X1 Carbon has had a lineage of consistent battery capacity increases, rising steadily generation by generation from the 1st (at 45.8Wh) up until the 5th generation, capping out at 57Wh and staying there for the 6th generation. Sadly, Lenovo decided that speakers were of more importance in a business laptop, and decided to make room for them by cutting the battery in this generation down to size by dropping it to 51Wh.

Fortunately, it does more than make up for it with the LPDT panel and a hexa-core processor. I would say that the savings and gains from the combined panel and hexa-core easily bring the newest generation of the Carbon above the previous generation in battery power when using it for lighter tasks.

For that reason, I am not as disappointed as I should be about this change, because the addition of the extra speakers are a nice touch, even if they feel sorely misguided and out of place in a business ultrabook. The speakers were indeed the weakest point of the previous generations, so this does round out the system slightly better overall.

When looking at moderate to heavy use, it of course all depends. When running the CPU in a custom TDP configuration and pushing against its thermal limits, you can drain the battery in under two hours. Under more moderate use and burst loads, expect to see 10W — 30W. Fairly average for ultrabooks, and you won’t see much change across any laptops in this category, as they are thermally limited to that range more than anything else, but you will see much better performance numbers in that power range.

Speakers

With the battery changes in mind, was the addition of the Dolby Atmos four speaker system worth it? Surprisingly — yes. If you have ever tried to listen to, well, anything!, on a previous generation X1 Carbon, you would quickly realize that it was damn near impossible. There is just about zero chance you’d be able to hear anything unless you were sitting in a dead quiet room with almost no ambient noise.

To say that the comparison between the new speakers and old are night and day would be an understatement. Aside from being more than three times as loud, they are very clear and incredibly high quality for a laptop system. While they won’t be competing with a real pair of headphones or any legitimate speaker setup, you might actually be able to listen to music or videos without grating your ears or wishing you could hear anything at all without putting your ears directly to the laptop. It is unfortunate that 6Wh of the battery capacity had to go to accommodate this change, but it does make this X1 Carbon much more well rounded. A surprisingly welcome change.

Performance

The main reason I purchased this device was its additional two cores, a 50% increase from the previous generation. For the uninitiated, scaling a CPU vertically (clock speeds) represents an exponential increase in power consumption due to the way voltage works. Being able to scale horizontally (with cores) allows a monumental power savings as long as your tasks are able to scale to take advantage of the extra cores. Fortunately, in the current year, with multiple tasks running and multiple threads being utilized by most applications, this is the case. We’ll be looking at the hexa-core i7-10710U CPU at four distinct power limit envelopes.

i7–10710U @ 10W (-125mV)

10 watts seems like a rather odd limit to be looking at, but it represents the distinct advantage of the hexa-core CPU compared to the previous generation. This happens to be superior performance to the previous four core generation X1 Carbon’s CPU performance at its rated 15 watt envelope. This is particularly important because it represents the biggest power savings under heavier loads the CPU will be seeing — a 33% decrease in power but about 10% better performance.

i7–10710U @ 15W (-115mV)

The next measurement shows us the performance at the chip’s officially rated limits. The additional 5 watts nets us a more than 17% gain in CPU performance against our 10 watt envelope, or a 30% gain against the four core generation of comparable Whiskey Lake U chips. For most medium usage, and the majority of multi-threaded games that can run on an integrated graphics card, 10W — 15W is going to be the sweet spot.

i7–10710U @ 25W (-100mV)

At 25 watts, we get what will likely be the most sustained performance you can get out of this device. While you can definitely go higher in bursts, you won’t be able to sustain it, as you will hit the thermal overhead quite quickly. You can crunch away all day at this performance level, without worrying about blowing up the laptop, or your lap. 10 additional watts nets us a 15% gain in CPU performance.

i7–10710U @ 45W (-80mV)

Finally, we see what kind of burst performance we can get while essentially maxing out the chip. With the undervolt, we are able to hit the 3.9GHz all-core, quite surprisingly, as the i7-8650U of the 6th generation Carbon took 44 watts to cap out on four cores with the same clock speeds. We are essentially getting those extra two cores of power “for free”, meaning these chips have been binned very well — and with the low volume of i7-10710U laptop sales, we can start to see why supply is low.

We get about 11% additional performance for our final 20 watts. The jump from 10 watts to 15 watts is >7x more efficient when it comes to power usage. With that said, lets take a look at the charts below to demonstrate why these extra two cores are so much more valuable this generation.

Voltage

Here we can see our scores versus power consumption plotted on a line graph. The more power we throw at it, the less efficient our additional power becomes. Normally, we would level out due to hitting a chip’s vertical scaling constraints (clock speed). In the case of recent laptops, this is generally not the case. Instead, we tend to level out due to hitting thermal limits. Thankfully, we can achieve a modest 30 watts sustained indefinitely before this occurs, which should wipe the floor with any desktop quad core chip not running some absurd cooling and overclocking. In most cases, we can still destroy desktop quad cores at just 15 watts.

On a six core system, voltage scaling is much tighter, but you will need much less voltage to get equal performance to that of a higher clocked quad core. With more cores, you can scale performance better with less change in voltage. We see this in action with our performance numbers above. The increase in voltage jumps as we increase our clocks, and we require more voltage faster. However, because we essentially get over “50%” more performance per voltage, our power consumption is much lower and we get much better performance per watt.

Conclusion

When people complain about Intel finally throwing on more cores into thin and light ultrabooks, or explain that six and eight cores in laptops are useless due to heat or battery usage, what they fail to understand is that this core improvement is beneficial for battery life in all non-extreme loads, and it is especially useful for daily use. Remember, you don’t have to run full throttle all the time, and in the majority of cases the extra cores help, not hurt! You can benefit from extra cores even while web browsing! To illustrate the point, we’ll see the raw difference in numbers between my two devices.

i7-8650U @ 15W

Here we have a score of 8544 at 15 watts by the i7-8650U in the previous generation X1 Carbon, with a similar single thread rating as our 10 watt score above. This gives us an efficiency of 569.6 points per watt for the quad core chip, compared to a whopping 952.3 points per watt on the i7-10710U. This makes the new chip 67% more power efficient while performing 10% better!

This is a better than linear increase with core count, thanks to the way voltage scaling works! For daily use, more cores scales in such a way that up until your applications can no longer fully utilize the extra cores, more cores means less power, more performance, less voltage, and more battery life! Business users and developers easily win the most here with the increased efficiency.

The battery and keyboard, while a downside compared to last generation, remain respectable given the performance and size of the device. With the addition of the LPDT display on top of the additional core count, we get back any battery life lost and then some. Verdict: The hexa-core Carbon delivers!