Dell XPS 13 2-In-1 (2019) Review: A Near-Perfect Intel 10th Gen Laptop
Dell XPS 13 7390: Battery, Thermal, and Acoustic Performance
To test battery life, we used a custom 1080p video running on loop until the system shuts itself down at 5%. Windows 10's Quiet Hours have been enabled to keep any extraneous notifications from stealing precious milliamp-hours of power, too. On each tested system, we calibrated the display to output as close to 115 lux as possible. We were able to get the display right down to 110 lux on the XPS 13 7390. This was two notches above the dimmest possible setting, so the display has plenty of dynamic range in its backlight. This system, like so many else on these charts, uses a 51 watt-hour battery, so there are no hidden advantages for Dell's convertible notebook.
In a word, battery performance is strong. This system keeps running much longer than most of the ultraportable systems we've tested in recent months, including Lenovo's ThinkPad X1 Carbon 7th gen and the earlier 2019 version of the non-convertible XPS 13 9380, despite this machine's much better overall performance. You'll have no problems getting through even long trans-continental flights with this system. The included 45-watt AC adapter will fill the battery back up in around 100 minutes, too.
The XPS 13 7390 didn't want to run its fans unless it absolutely had to. That means in our first Cinebench R20 run, the fan didn't even kick on until we hit the CPU's maximum allowed temperature of 100 degrees Celsius. Once the fans kicked in, the CPU was able to maintain a clock speed of 2.7 GHz on all four threads for the remainder of the first run and the entirety of the second. Even better, once the fans were in gear, the temperatures dropped below the ragged maximum and settled around 82 degrees Celsius. That's quite warm, but in laptop mode while plugged in, the bottom of the machine was only warm to the touch.
The fans with the system plugged in were audible, but not very loud at all. To test acoustic performance we used a sound meter on our trusty Samsung Galaxy S10 Plus. Our approximately 30 decibel room felt dead silent to us, and while we could hear the fans spin up in the XPS 13, they were never annoying. The sound meter registered between 33 and 35 decibels for the length of the second Cinebench run. It didn't matter where we set the phone, but we chose to place it to the side of the notebook since the vents are in the top of the open base, above the keyboard. That should have gotten the phone as close to the fans as possible. Just as important as the noise volume, the noise character was an unobtrusive woosh of white noise, not a high-pitched turbine whine or squeal.
Performance dropped precipitously on this test, though, as the unplugged system scored a mere 907 on the multi-threaded test. That's down a full 50% from being plugged in. Despite that drop, performance was never sluggish while we browsed the web, typed up this article, and used Excel to make the charts for the performance section. That power conservation paid off in the thermal department, though–the package temperature never exceeded 53 degrees Celsius for the duration of either run, and the fans never kicked on at all while sitting on our legs, and it never felt uncomfortably warm. Even sitting on a throw pillow, which completely obstructed the vents, wasn't enough to make the fans run while watching videos or getting the article written.
Now that we've looked at everything in detail, let's tie it all together and render our final verdict.
In a word, battery performance is strong. This system keeps running much longer than most of the ultraportable systems we've tested in recent months, including Lenovo's ThinkPad X1 Carbon 7th gen and the earlier 2019 version of the non-convertible XPS 13 9380, despite this machine's much better overall performance. You'll have no problems getting through even long trans-continental flights with this system. The included 45-watt AC adapter will fill the battery back up in around 100 minutes, too.
Dell XPS 13 7390 Acoustics and Thermals
Most tablet PC users would appreciate it if the PC didn't get so hot as to burn them. While it's unlikely a user would drive such a convertible PC to the ragged edge for extended periods making it too hot to touch, we test every machine to come through our labs for the worst-case real world scenario. Nobody will run Prime95 full-time on a portable notebook, and so we test with a full Cinebench R20 load. We ran two passes of the benchmark–the first to warm up the systems and the second to monitor clock speeds, temperatures, and noise.The XPS 13 7390 didn't want to run its fans unless it absolutely had to. That means in our first Cinebench R20 run, the fan didn't even kick on until we hit the CPU's maximum allowed temperature of 100 degrees Celsius. Once the fans kicked in, the CPU was able to maintain a clock speed of 2.7 GHz on all four threads for the remainder of the first run and the entirety of the second. Even better, once the fans were in gear, the temperatures dropped below the ragged maximum and settled around 82 degrees Celsius. That's quite warm, but in laptop mode while plugged in, the bottom of the machine was only warm to the touch.
Performance and Temperatures Unplugged
80 degrees Celsius is too hot to use as a tablet, but you're probably not going to handle the system in tablet mode with it plugged in. To get a feel for how much performance we give up by running on battery power and find out how much thermal load we can save, we performed back-to-back Cinebench R20 runs on battery power too. According to the Package Power statistic in HWMonitor, the CPU drew just 10 watts of energy. HWMonitor said the CPU still hung just short of 3 GHz, but the app samples CPU speeds once per second, where a modern CPU can oscillate frequencies many times per second.
Half-way through the first run while unplugged. the XPS 13 7390 still hadn't hit 50 degrees Celsius
Performance dropped precipitously on this test, though, as the unplugged system scored a mere 907 on the multi-threaded test. That's down a full 50% from being plugged in. Despite that drop, performance was never sluggish while we browsed the web, typed up this article, and used Excel to make the charts for the performance section. That power conservation paid off in the thermal department, though–the package temperature never exceeded 53 degrees Celsius for the duration of either run, and the fans never kicked on at all while sitting on our legs, and it never felt uncomfortably warm. Even sitting on a throw pillow, which completely obstructed the vents, wasn't enough to make the fans run while watching videos or getting the article written.
Now that we've looked at everything in detail, let's tie it all together and render our final verdict.
