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Low Power Mode for Mac laptops: making the case again

Written by Marco Ament / Original link on Jan. 13, 2020

In light of today’s rumor that a Pro Mode may be coming that seems to offer benefits in the opposite direction,1 I wanted to re-make the case for a Low Power Mode on macOS — and explain why now is the time.

Modern hardware constantly pushes thermal and power limits, trying to strike a balance that minimizes noise and heat while maximizing performance and battery life.

Software also plays a role, trying to keep everything background-updated, content-indexed, and photo-analyzed so it’s ready for us when we want it, but not so aggressively that we notice any cost to performance or battery life.

Apple’s customers don’t usually have control over these balances, and they’re usually fixed at design time with little opportunity to adapt to changing circumstances or customer priorities.

The sole exception, Low Power Mode on iOS, seems to be a huge hit: by offering a single toggle that chooses a different balance, people are able to greatly extend their battery life when they know they’ll need it.2

Mac laptops need Low Power Mode, too. I believe so strongly in its potential because I’ve been using it on my laptops (in a way) for years, and it’s fantastic.

I’ve been disabling Intel Turbo Boost on my laptops with Turbo Boost Switcher Pro most of the time since 2015.

In 2018, I first argued for Low Power Mode on macOS with a list of possible tweaks, concluding that disabling Turbo Boost was still the best bang-for-the-buck tweak to improve battery life without a noticeable performance cost in most tasks.3

Recently, as Intel has crammed more cores and higher clocks into smaller form factors and pushed thermal limits to new extremes, the gains have become even more significant. Here’s some thermal testing from my 8-core 16-inch MacBook Pro:

16-inch MacBook Pro (Late 2019, 2.4 GHz 8-core i9)

Power Temp. Geekbench 5 single/multi xcodebuild
Normal 82W 90°C 1260/7386 39 sec.
No Turbo 31W
−62%
65°C 669/5206
−46/29%
62 sec.
+59%

With Turbo Boost disabled, peak CPU power consumption drops by 62%, with a correspondingly huge reduction in temperature. This has two massive benefits:

I haven’t done formal battery testing on the 16-inch, since it’s so difficult and time-consuming to do in a controlled way that’s actually useful to people, but anecdotally, I’m seeing similar battery gains by disabling Turbo Boost that I’ve seen with previous laptops: significantly longer battery life that I’d estimate to be between 30–50%.

This comes at a cost to performance, but:

The vast majority of the time I’m using it, the 16-inch MacBook Pro is a much better laptop with Turbo Boost disabled.

It’s still fast enough to do everything I need (including significant development with Xcode), while remaining silent and cool, with incredible battery life.

But soon, I bet I won’t be able to do this anymore.

Turbo Boost Switcher Pro relies on a kernel extension that’s grandfathered into Apple’s latest security requirements, but it can never be updated — and when macOS Catalina loads it for the first time, it warns that it’ll be “incompatible with a future version of macOS.” I suspect that this is the last year I’ll get to run the latest OS and be able to turn off Turbo Boost at will, making all of my future laptop usage significantly worse.

Please, Apple, make this feature official: give us a Low Power Mode for macOS that disables Turbo Boost to keep our laptops cool, quiet, and long-lasting at times when those are more important to us than speed.

  1. My guess is that “Pro Mode” doesn’t raise the peak performance, but instead raises the fan speeds to allow longer sustained operation at high Turbo Boost speeds. ↩︎

  2. Low Power Mode has been so successful on iOS that Apple also thought it worthwhile to add a Low Data Mode to iOS 13, offering similar control over data usage. (Mac owners can get similar functionality with the excellent TripMode.) ↩︎

  3. As I wrote back then, disabling discrete GPUs and Photos analysis are other obvious contributors to a good Mac Low Power Mode. ↩︎

marcoament

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