Low Power Mode for Mac laptops: making the case again
Low Power Mode for Mac laptops: making the case again – Marco.org

                        
                                                            
                                    Low Power Mode for Mac laptops: making the case again
                                                                    
                            
                            
                                January 13, 2020
                                ∞https://marco.org/2020/01/13/macos-low-power-mode-redux
                            
                        
                    
                        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:


The fans never audibly spin up. When Turbo Boost is enabled, the fans annoyingly spin up every time the system is under a heavy sustained load. Disable it, and it’s almost impossible to get them to be audible.
It runs significantly cooler. Turbo Boost lets laptops get too hot to comfortably hold in your lap, and so much heat radiates out that it can make hands sweaty. Disable it, and the laptop only gets moderately warm, not hot, and hands stay comfortably dry.


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:


It’s not noticeable on most workloads.
Parallel workloads are affected far less than single-threaded tasks, and most modern heavy workloads are parallelized.
This is an 8-core laptop that’s competitive with my iMac Pro! It’s much faster than most people need (myself included) most of the time, so I can spare some performance to get other benefits.

A fast laptop isn’t very useful if your hands are too sweaty to type, the battery dies in the middle of a flight, or the loud fans ruin your audio recording.
When I really want to maximize performance, Turbo Boost Switcher Pro lets me quickly toggle it in the menu bar, so switching between modes is easy.


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.


                    