If I use the CPU heavily while charging a Mac, how much slower will the charging be? It would be interesting to hear if someone has data how many minutes it takes to:
- Charge 0-100% while using ~0% CPU
- Charge 0-100% while using 100% CPU
PS! Another interesting question (probably a separate question) would be: If a heavy 100% CPU job takes 1 hour on a 100% charged machine, how long does it take on a charging machine?
Best Answer
The CPU is boss of the power scheme and will get all the power it requests. The charger is boss of the maximum power it will output.
The CPU can pull from two sources and the charger can deliver to two sources.
It’s a pretty simple systematic first glance, but the nonlinear charge and variable CPU/GPU loads make si ole linear time estimates not match reality.
So, if your charger is not providing the power needed to keep the CPU fully powered, the battery will drain and eventually the Mac will shut off because there’s no more battery to make up the deficit in power. And that is why the CPU can run at full speed.
I don’t think there is any general common timing even if you restrict yourself to only USB-C charging models. But, the great news is you can just open the terminal and check the current power budget and time estimates and not rely on me or anyone else rule of thumb on the internet.
Those three commands show engineering summaries and details for the overview of the system state (sysloadlog) and the thermal CPU throttling (thermlog). The last power log will answer the specifics of any charge scenario for any model Mac and the charger you have connected.