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[OS X] How does this sleep scenario actually work?

Message #1 - Posted 2002/02/06 - John Steinberg

Details:

G4/533 DP with an external FW HD that has the OS X 10.1.2 boot system. At night I sleep the machine, via the Apple menu, and physically turn off the external HD (because it will not sleep.)

And yet, in the morning I can awaken the machine, and see the Finder with the clock ticking away - although still on the previous nights time - and only then turn on the external HD and within moments the clock updated to current time, and everything on the computer works perfectly well as if nothing ever happened.

I know FW is hot-pluggable, but is the OS X system fully stored in the RAM to allow for this seemingly amazing bit of prestidigitation?

Perhaps this is a naïve question, but it amazes me daily! (and yes, I have a very low entertainment threshold.)

Any insight to the processes involved would be most welcome.

-John Steinberg -------------------------------------------------------------- email: manbytsdog at aol dot com | http://nexstar.50megs.com/

Message #2 - Posted 2002/02/06 - ZnU

Previously, John Steinberg wrote:

Details:

G4/533 DP with an external FW HD that has the OS X 10.1.2 boot system. At night I sleep the machine, via the Apple menu, and physically turn off the external HD (because it will not sleep.)

And yet, in the morning I can awaken the machine, and see the Finder with the clock ticking away - although still on the previous nights time - and only then turn on the external HD and within moments the clock updated to current time, and everything on the computer works perfectly well as if nothing ever happened.

I know FW is hot-pluggable, but is the OS X system fully stored in the RAM to allow for this seemingly amazing bit of prestidigitation?

Yes. This is basically how sleep works. The contents of RAM are preserved, just about everything else shuts down.

Newer hardware also supports a sleep mode where the contents of RAM are written out to disk (so even the RAM goes unpowered in sleep) and loaded back when the system wakes up. I don't think either OS 9 or OS X take advantage of this yet. But you probably wouldn't want to use it anyway; sleep and wakeup times would be a lot longer. It might be worth it on laptops for the extra power savings, I guess.

Perhaps this is a naïve question, but it amazes me daily! (and yes, I have a very low entertainment threshold.)

Any insight to the processes involved would be most welcome.

"We are living in a world today where lemonade is made from artificial flavors, and furniture polish is made from real lemons." --Alfred E. Newman

Message #3 - Posted 2002/02/06 - John Steinberg

ZnU wrote:

Yes. This is basically how sleep works. The contents of RAM are preserved, just about everything else shuts down.

Has this always been the case? I think this fascinates me because doing the same (IIRC and I may not) on an external SCSI HD, under systems prior to OS X, could be catastrophic.

Newer hardware also supports a sleep mode where the contents of RAM are written out to disk (so even the RAM goes unpowered in sleep) and loaded back when the system wakes up. I don't think either OS 9 or OS X take advantage of this yet. But you probably wouldn't want to use it anyway; sleep and wakeup times would be a lot longer. It might be worth it on laptops for the extra power savings, I guess.

Very interesting. Thank you!

-John Steinberg -------------------------------------------------------------- email: manbytsdog at aol dot com | http://nexstar.50megs.com/

Message #4 - Posted 2002/02/06 - Peter Seebach

Previously, John Steinberg wrote:

Has this always been the case? I think this fascinates me because doing the same (IIRC and I may not) on an external SCSI HD, under systems prior to OS X, could be catastrophic.

Probably because SCSI wasn't hot-pluggable on old Mac implementations. (Some modern SCSI systems are.)

-s

Copyright 2001, all wrongs reversed. Peter Seebach / seebs@plethora.net $ chmod a+x /bin/laden Please do not feed or harbor the terrorists. C/Unix wizard, Pro-commerce radical, Spam fighter. Boycott Spamazon! Consulting, computers, web hosting, and shell access: http://www.plethora.net/

Message #5 - Posted 2002/02/06 - ZnU

Previously, John Steinberg wrote:

ZnU wrote:

Yes. This is basically how sleep works. The contents of RAM are preserved, just about everything else shuts down.

Has this always been the case?

Laptops have done this practically forever.

Older desktop systems didn't support "real" sleep. They just put their screens in power-saving mode and spun down their hard drives. This changed with (IIRC) the Sawtooth G4s and the rev. C iMacs.

I think this fascinates me because doing the same (IIRC and I may not) on an external SCSI HD, under systems prior to OS X, could be catastrophic.

SCSI isn't hot-pluggable. (Well, not outside of fancy server implementations, anyway.) Plugging and unplugging devices or turning them and or off can cause strange electrical signals to be sent through the chain, confusing the hell out of devices, and possibly even damaging them (though that doesn't happen much).

On systems with real sleep support (basically just laptops until a couple of years ago), you could plug and unplug SCSI devices while the system was sleeping, since the SCSI port was inactive and unpowered in sleep.

FireWire and USB are, of course, totally hot-pluggable, and the OS is smart enough to automatically detect new devices (and load the appropriate drivers, if it has them) as soon as they're connected.

Newer hardware also supports a sleep mode where the contents of RAM are written out to disk (so even the RAM goes unpowered in sleep) and loaded back when the system wakes up. I don't think either OS 9 or OS X take advantage of this yet. But you probably wouldn't want to use it anyway; sleep and wakeup times would be a lot longer. It might be worth it on laptops for the extra power savings, I guess.

Very interesting. Thank you!

"We are living in a world today where lemonade is made from artificial flavors, and furniture polish is made from real lemons." --Alfred E. Newman

Message #6 - Posted 2002/02/06 - Cathy Stevenson

Previously, John Steinberg wrote:

Details:

G4/533 DP with an external FW HD that has the OS X 10.1.2 boot system. At night I sleep the machine, via the Apple menu, and physically turn off the external HD (because it will not sleep.)

<snip>

On the off-chance that your external drive is a Maxtor FW, there are now drivers for it that allow it to sleep. I inadvertently found tthem yesterday at the Maxtor site while troubleshooting a problem with my Maxtor.

Cathy

""If we don't alter our course, we're going to end up where we're headed." - Chinese proverb

C.Stevenson, M.D.
cats1921@bayarea.net

Message #7 - Posted 2002/02/06 - John Steinberg

cats192 wrote:

On the off-chance that your external drive is a Maxtor FW, there are now drivers for it that allow it to sleep. I inadvertently found tthem yesterday at the Maxtor site while troubleshooting a problem with my Maxtor.

Alas it's not, but that's a great heads up for those who are using Maxtor drives (thus my repeating it here.)

Appreciate the feedback from all!

-John Steinberg -------------------------------------------------------------- email: manbytsdog at aol dot com | http://nexstar.50megs.com/

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