The Turbo Boost modes designed by Intel and AMD are a way of delivering high performance in burst workloads without running the CPU at a constant high clock. What’s less known is that this feature comes with a massive hit to battery life, at least on Intel systems. I’m not trying to imply that AMD laptops don’t have a similar issue — I just haven’t tested the impact of disabling Turbo Mode on an AMD notebook.
Developer Marco Ament has written a blog post on the impact of disabling TurboBoost on his 16-inch MacBook Pro, and the difference is significant:
This graph addresses temperature, power, and performance (we’ll get to battery life). As you can see, power consumption falls 62 percent, temperatures are lower, and overall performance takes a hefty whack. The trade-off is nearly linear in the case of xcodebuild, while Geekbench 5’s performance declines by less than the overall power reduction.
The tradeoff, however, is significantly increased battery life. Marco didn’t do a formal test due to the intrinsic difficulty of creating real-world benchmarks, but he estimates his 16-inch MacBook gets 30-50 percent better battery life with Turbo Boost disabled. The other major advantage? Virtually no fan noise, even under full load.
Here’s where I want to pivot and talk about my own experience with this trick. I have an Alienware R13
from 2016. When new, it got roughly two hours of battery life in normal use. Video playback was a bit better, but the laptop has a GTX 1060 in it, and GPU-equipped machines always use more power. I figured two hours was all you could expect to get out of a gaming laptop, but since I wanted more battery for long flights, I decided to test the impact of changing the Turbo Boost parameters to see what would happen. I used Intel’s XTU utility for this, but there are other ways to disable Turbo Boost, including programs like Throttlestop.
The advantage of using Intel’s XTU was that I got more granularity to play with the actual Turbo Boost settings, though this utility isn’t supported on every Intel laptop. Some laptops may also offer UEFI options for adjusting Turbo Boost timing and parameters, though laptop UEFI is typically more locked-down than desktop parts. You can check the list of supported CPUs for XTU here, but not every chip is listed — the 7700HQ itself, for example, isn’t.
XTU running on a 7700HQ.
Assuming you have access to XTU and you’re willing to muck around with your laptop’s power configuration (completely at your own risk), you can actually achieve some astonishing improvements at the cost of making a system incredibly slow. When I travel, I’ll often tighten various amperage and power settings until the laptop is locked at 800MHz. I’m not even going to pretend that the user experience is good in this configuration, as the machine is slow enough to visibly lag. I can write stories or alt-tab between a document and a PDF to make slides and I can still play movies and TV shows flawlessly, but it’s not particularly useful for anything else.
Why do I bother? Because it virtually triples the runtime I get out of the laptop when watching video or doing basic desktop work, and the amount of time I gain is orders of magnitude larger than the time I spend waiting on the PC (the lag is detectable, but it’s well under a second). I wish I had a formal benchmark to show — like Marco, I don’t — but I have timed the actual run-time I got on an airplane while watching movies, and clocked it as just short of six hours, compared to a little over two for the standard configuration.
I want to be very clear here: I’m not just disabling Turbo Boost to get that kind of improvement. To hit that target, I’m throttling the CPU to within an inch of its life by using XTU to lower the 7700HQ’s default voltage and IccMax. The reason I’m bringing it up is to demonstrate that the 30-50 percent battery life improvement that Marco Ament is talking about isn’t a crazy claim. If I can nearly triple a machine’s battery life by aggressive throttling and voltage changes, I can easily believe a 30-50 percent improvement just from disabling Turbo Boost.
The Clockspeed Caveat
There is, however, one reason why low-power laptop users might want to avoid this kind of trick. The 9980HK in Marco’s laptop has a base clock of 2.4GHz and a boost clock of 5GHz. If you turn off Turbo Mode, your CPU will run at a maximum of 2.4GHz on all eight cores. An eight-core Intel Core i9 does pretty well at just 2.4GHz, and Marco reports being pretty satisfied with performance.
If you turn off Turbo Boost on, say, the new Intel Surface Laptop 3 with a Core i7-1065G7, you’re going to wind up at a much lower base clock. I tested the Surface Laptop 3 in Cinebench R20 with Turbo Boost enabled and disabled. With Turbo Mode enabled, the CPU turned in a score of 1689 for multi-core and 434 for single-core. That’s mostly in line with expectations, though the single-core performance was a bit low. With Turbo on, the CPU bursts up to 3.5GHz before settling back down to 2.7 – 2.8GHz. Single core boosts up to 3.67GHz in our test run.
Without Turbo Boost, the laptop sits at 1.3GHz no matter what, whether it’s running single-core or all-core. Multi-core performance falls from 1689 to 743, a drop of 43 percent. The relatively low base clock speed on Ice Lake 15W CPUs means you don’t have nearly as much performance to work with once Turbo Boost is off, while the smaller number of CPU cores means you can’t lean as heavily on parallelism to keep performance up. Single-core performance drops from 434 to 158, a drop of 64 percent.
I like using Throttlestop or XTU for this kind of manipulation, but there are other methods. There’s no magic to the idea of down-clocking your CPU to save battery, but the benefits are larger than people might expect. If you find yourself on a long flight with a need to conserve charge, I’d recommend it. Keep in mind that the impact of hauling a 45W CPU with a base clock of 2.8GHz down to 800MHz via XTU will be larger than the improvement from disabling Turbo Boost on a 15W chip.
To be clear, there’s nothing wrong with Turbo Boost. It functions as designed, and it improves laptop performance while using less battery (and making less noise) than running the chip at full clock all day long. Tweaks like this allow you to throw the lever all the way towards saving power, over and above what Windows makes available by default, but there’s nothing broken about Intel’s implementation of Turbo Boost or AMD’s Turbo Mode.
Now Read:
- Intel Talks Foldable Laptops,5G, Xe, and Tiger Lake at CES 2020
- AMD and Intel Go Head to Head in the Surface Laptop 3
- 8-Core AMD Ryzen 4000 Mobile APUs Launching in Q1 2020 With 15W, 45W Chips
from ExtremeTechExtremeTech https://ift.tt/2tnEhLc
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