Questions about OS X and sleep

in macOS edited January 2014
I've tried searching Google Groups and this BB in to get a better understanding of how sleep works in OS X... but all I tend to find is people talking about problems with sleep: My computer won't sleep, my computer suddenly falls asleep while I'm using it, my computer wakes from sleep and destroys Western Civilization, etc.

What I'm curious about is what level of activity, if any, goes on while my Mac, running OS X (soon to be Jaguar, later tonight!), is sleeping.

I know that OS X, being Unix based, likes to run 24/7 rather than being on a computer that's turned off a lot of the time. But is sleep much better than being turned off? Can cron jobs and routine system maintenance tasks get done by a sleeping OS X? If my hard drive is set to spin down during sleep, will it spin back up as needed for system tasks?

I've heard of products like MacJanitor being recommended for those who shut off their Macs entirely, but only in one description of MacJanitor that I've read was sleep mentioned. In this instance, someone made it sound like cron jobs and system maintenance DON'T happen on a sleeping OS X system any more than they do on one that's entirely shut down.

What's the real story on sleep? Since I do leave my computer (a TiBook 800) switched on nearly all the time, but also sleeping most of that time, should I get MacJanitor or something like it? Will Jaguar perhaps give me more control over how deep sleep is, or at least obviate the need for a MacJanitor-like product?


  • Reply 1 of 1
    der kopfder kopf Posts: 2,275member
    IMHO, during sleep virtually nothing happens. Your memory modules get a little power. And that's about it. For what is the difference between waking up from sleep and starting up: with the first, you just 'turn on' all sleeping parts of your computer: hard disk, screen, processor(?), and this mainly based on information in your RAM - which has to be powered if it is to keep its contents -. During startup, you actually load system-information into your RAM, so you can get a speedy comp. (you might now that the HD can be up to 15 million times slower than RAM memory.)

    Main point in all this: your RAM has to be powered all the time in sleep, but I'm pretty sure the rest of your computer does nothing -no cron jobs, no nothing-.
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