Comment by withinboredom

4 years ago

> Not really a problem when your computer has a large UPS built into it.

Except that _one time_ you need to work until the battery fails to power the device, at 8%, because the battery's capacity is only 80%. Granted, this is only after a few years of regular use...

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withinboredom

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monocasa  4 years ago

In Apple's defense, they probably have enough power even in the worst case to limp along enough to flush in laptop form factor, even if the power management components refuse to power the main CCXs. Speccing out enough caps in the desktop case would be very Apple as well.

  • marcan_42  4 years ago

    Apple do not have PLP on their desktop machines (at least not the Mac Mini). I've tested over 5 seconds of written but not FLUSHed data loss, and confirmed via hypervisor tracing that macOS doesn't do anything when you yank power. It just dies.

  • withinboredom  4 years ago

    Once voltage from the battery gets too low (despite reporting whatever % charge), you aren't getting anything from the battery.

    • monocasa  4 years ago

      It's the other way around. The PMIC cuts the main system off at a certain voltage, and even in the worse case you have the extra watt/sec to flush everything at that point.

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    • marcan_42  4 years ago

      Batteries don't die instantly; you always have a few seconds where voltage is dropping fast and can take emergency action (shut down unnecessary power consumers, flush NVMe) before it's too late. Weak batteries die by having higher internal resistance; by lowering power consumption, you buy yourself time.

      I don't know if macOS explicitly does this, but it does try to hibernate whem the battery gets low, and that might be conservative enough to handle all normal cases.

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