Alienware 15 R2

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The Turbo Boost modes designed by Intel and AMD are a way to deliver high performance in burst workloads without running the CPU on a consistently high clock. What is less known is that this feature has a huge impact on the life of the battery, at least on Intel systems. I’m not trying to imply that AMD laptops don’t have a similar problem – I just didn’t test the impact of turning off Turbo mode on an AMD notebook.

Developer Marco Ament has written a blog post about the impact of turning off TurboBoost on his 16-inch MacBook Pro, and the difference is significant:

This graph relates to temperature, power and performance (we are about the battery life). As you can see, power consumption drops by 62 percent, the temperatures are lower and overall performance takes a big blow. The trade-off is almost linear in the case of xcodebuild, while the performance of Geekbench 5 decreases less than the overall power reduction.

However, the trade-off is a considerably longer battery life. Marco has not taken a formal test due to the intrinsic difficulty of making real benchmarks, but he estimates that his 16-inch MacBook will get a 30-50 percent better battery life with Turbo Boost disabled. The other big advantage? Virtually no fan noise, even at full load.

Here I want to run and talk about my own experience with this trick. I have an Alienware R13 from 2016. When it was new, it got about two hours of battery life under normal use. Video playback was slightly better, but the laptop has a GTX 1060 and machines equipped with GPU always use more power. I thought two hours was the only thing you could expect from a gaming laptop, but because 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 the Intel XTU utility for this, but there are other ways to disable Turbo Boost, including programs such as Throttlestop.

The advantage of using Intel’s XTU was that I got more granularity to play with the actual Turbo Boost settings, although this utility is not supported on every Intel laptop. Some laptops may also offer UEFI options for adjusting Turbo Boost timing and parameters, although laptop UEFI is generally more locked than desktop components. You can view the list of supported CPUs for XTU here, but not every chip is listed – the 7700HQ itself, for example.

XTU runs on a 7700HQ.

Assuming you have access to XTU and you are willing to mess with the power configuration of your laptop (completely at your own risk), you can achieve some amazing improvements at the expense of making a system incredibly slow. When I am traveling, I will often adjust various current and energy settings until the laptop is locked at 800 MHz. I am not even going to pretend that the user experience is good in this configuration, because the machine is slow enough to remain visible. I can write stories or alt-tabs between a document and a PDF to make slides and I can still play movies and TV programs flawlessly, but it’s not particularly useful for anything else.

Why should I worry about that? Because it almost triples the runtime I get from the laptop when I watch video or do standard desktop work, and the amount of time I win is an order of magnitude greater than the time I spend on the PC (the delay is detectable, but it is more than a second). I wish I had a formal benchmark to show – like Marco, not me – but I timed the actual runtime I got on an airplane while watching movies, and clocked it for only six hours, compared to a little more than two for the standard configuration.

I want to be very clear here: I don’t just switch off Turbo Boost to get improvements like that. To achieve that goal, I limit the CPU to an inch of its life by using XTU to lower the standard voltage of the 7700HQ and IccMax. The reason why I bring it up is to show that the 30-50 percent improvement in battery life that Marco Ament is talking about is not a crazy claim. If I can almost triple the battery life of a machine through aggressive throttling and voltage changes, I can easily believe a 30-50 percent improvement, just by turning off Turbo Boost.

The Clockspeed Caveat

However, there is a reason why low-power laptop users want to avoid this kind of trick. The 9980HK in the Marco laptop has a basic clock of 2.4 GHz and a boost clock of 5 GHz. If you disable Turbo mode, your CPU will run at a maximum of 2.4 GHz on all eight cores. An eight-core Intel Core i9 is doing pretty well at just 2.4 GHz and Marco reports being quite satisfied with the performance.

If you switch off Turbo Boost, for example the new Intel Surface Laptop 3 with a Core i7-1065G7, you will end up with a much lower basic clock. I tested the Surface Laptop 3 in Cinebench R20 with Turbo Boost on and off. With the Turbo mode on, the CPU achieved a score of 1689 for multi-core and 434 for single-core. That is usually in line with expectations, although the single-core performance was a bit low. With Turbo on, the CPU bursts up to 3.5 GHz before going back to 2.7 – 2.8 GHz. Single core increases to 3.67 GHz during our test run.

Without Turbo Boost, the laptop is at 1.3 GHz, whatever happens, whether it is single-core or all-core. Multi-core performance drops from 1689 to 743, a decrease of 43 percent. The relatively low basic clock speed on Ice Lake 15W CPUs means that you will not have nearly as much performance to work with once Turbo Boost is off, while the smaller number of CPU cores means that you cannot rely so heavily on parallelism to maintain performance up . Single-core performance fell from 434 to 158, a decrease of 64 percent.

I like to use Throttlestop or XTU for this kind of manipulation, but there are other methods. There is no magic in the idea to down-clock your CPU to save the battery, but the benefits are greater than people would expect. If you are on a long flight with a need to save costs, I would recommend it. Keep in mind that the impact of transporting a 45W CPU with a basic clock from 2.8 GHz to 800 MHz via XTU will be greater than the improvement of disabling Turbo Boost on a 15W chip.

To be clear, there is 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 on full clock all day. With tweaks like this, you can throw the handle all the way to saving energy, on top of what Windows makes available as standard, but there’s nothing wrong with the implementation of Turbo Boost by Intel or the Turbo Mode of AMD.

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