Difference between shutdown and restart?

[hierobryan]

What's the difference? My old boss told me that when you shutdown and wait about 10 seconds the computer will clear some kind of cache, which doesn't happen when you restart...but he was talking about PCs, so maybe it's different for Macs?
I work in a PC computer lab, and the people I report to tell me to shutdown and NOT restart when I open and close the lab.

 

[iCeFuSiOn]

A shutdown simply powers down the machine almost entirely and does not attempt to start the operating system again until you press the power button. A restart simply ends your session in Mac OS X, shuts the operating system down, and then re-loads the operating system again.

 

[hierobryan]

A shutdown simply powers down the machine almost entirely and does not attempt to start the operating system again until you press the power button. A restart simply ends your session in Mac OS X, shuts the operating system down, and then re-loads the operating system again.

duh, i know that. i mean is there any kind of cache or memory the computer clears/does not clear?

 

[iCeFuSiOn]

duh, i know that. i mean is there any kind of cache or memory the computer clears/does not clear?

Not that I am aware of.

 

[Techguy172]

It clears lot's of caches such as processor hard drive and Memory

 

[hierobryan]

ahhhhh....now i'm wondering why so many people let their macs run and run and run with only a restart here and there.

 

[bogman12]

shutdown is used with the intention of leaving the computer in an off stage once the shutdown procedure has completed.

restart is used with the intention of recycling the current session of the OS, to reset applications running/hanging etc..

 

[srl7741]

I supervise a Forensic Computer lab and would venture to guess the reason for their request would amount to this?

Shutting down will prevent theft and data loss issues among other things. Re-starting will leave your computers available or open to many other risks.

There are a number of reason why they may request that actually.

Work stations should be shut down unless you are still running programs that process data that require hours to complete. It goes without saying if you shut down the machine the programs running will not complete their task and in the AM you will have to start over.

I guess it will depend on the kind of lab and the purpose of each machine. Each machine may have a different purpose and that will dictate weather it needs to be shut down completely or not.

 

[JNB]

Short answer, no effective difference.

A restart (at least in a Unix environment, which the Mac is), dumps EVERYTHING, and boots fully from a zeroed state. ALL processes are released and reinitiated from scratch. Even if there were anything residual in any cache, it would be overwritten anyway when the system was being restored.

I think the theory being put forward is that since some of the caps haven't fully bled off, there may be residual data in some of the registers. Unless they can state absolutely the decay rate of those, then "ten seconds", or any other SWAG'd delay, is basically bollocks.

This is more ancient technology concept, and since most Windows users have NEVER seen what actually goes on, process-wise, in detail, it's become more computer urban legend/dogma than anything else.

You could posit that a restart is easier on the microelectronics as they don't have time to suffer from thermal expansion because of short-cycle cooling & reheating. That, as well, is debatable, but certainly a stronger theoretical argument than any nebulous "data left in cache" claim.

 

[k9gardner]

Short answer, no effective difference.

A restart (at least in a Unix environment, which the Mac is), dumps EVERYTHING, and boots fully from a zeroed state. ALL processes are released and reinitiated from scratch. Even if there were anything residual in any cache, it would be overwritten anyway when the system was being restored.

I think the theory being put forward is that since some of the caps haven't fully bled off, there may be residual data in some of the registers. Unless they can state absolutely the decay rate of those, then "ten seconds", or any other SWAG'd delay, is basically bollocks.

This is more ancient technology concept, and since most Windows users have NEVER seen what actually goes on, process-wise, in detail, it's become more computer urban legend/dogma than anything else.

You could posit that a restart is easier on the microelectronics as they don't have time to suffer from thermal expansion because of short-cycle cooling & reheating. That, as well, is debatable, but certainly a stronger theoretical argument than any nebulous "data left in cache" claim.

This may be true in Windows but not entirely true in macOS. I have just ended up with an as-yet unsolved situation on an old Mac mini (Late 2012), in which I have just replaced the HDD with a SSD, installed a clean install of exactly the same OS that was on it previously (Catalina 10.15.7) and on every restart it fails with the “no” or “prohibited” symbol (which I didn’t even know about before this!), indicating that the operating system present is not able to be run (as in an OS too recent for the computer). However, on a power-off startup, it works just fine. I then decided to restore from the previous HDD rather than doing a clean install, with the same results.

I don’t yet know why this is happening, but I can assure you that a system restart does not do the same thing as a full power-off startup.