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10.5: Enable nap mode in 10.5 on G4 MDD systems Desktop Macs
Some G4 Mirrored Drive Door (MDD) systems have cooling systems that run loudly as the CPUs get hot, especially the model affectionately known at the "Windtunnel" G4s. On those systems, enabling nap mode brings the normal operating temperature down remarkably well, thereby quieting the fans. This was covered in this older hint.

The method is basically to install the last version of Apple's C.H.U.D. tools that allows Nap Mode on those machines, which is version 3.5.2 [21MB download]. That version still works with Leopard, although notably it misreports cache sizes. However, the old command line utility, and therefore the derived AppleScripts, that people have relied on until now to enable nap mode have broken.

So here is an Applescript I wrote that will enable nap mode again, even under Leopard: Ideally the next version of C.H.U.D. Tools would bring Nap Mode back for these models which need it. Merciful Apple, why have you taken it away?
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10.5: Enable nap mode in 10.5 on G4 MDD systems | 9 comments | Create New Account
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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: sipatel on Nov 15, '07 07:11:51PM

Just what I have been looking for.

Now, when will someone come up with a way to get rid of the sidebar in Leopard?



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: kaylan on Nov 16, '07 06:58:42AM

Cool trick. However, it also defaults back to 2 cpus instead of one even if you had preselected one. Two CPUs in nap mode will eventually crash the machine. However, if I switch to single cpu when turning on the nap mode, it will not crash. How to switch to single CPU inside of the same script?



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: theusjones on Nov 16, '07 12:05:27PM

So this is for a single CPU MDD machine then?


Adding this line to the script ought to do it:

click radio button "Single CPU" of radio group 1 of window "Hardware"


Which makes the script go like so:

tell application "System Preferences"
activate
set current pane to pane "Hardware"
tell application "System Events"
if not UI elements enabled then
display dialog "GUI Scripting is not enabled. Enable?"
set UI elements enabled to true
end if
tell application process "System Preferences"
set napModeBox to checkbox 1 of group 1 of window "Hardware"
if value of napModeBox is 0 then
click napModeBox
end if
click radio button "Single CPU" of radio group 1 of window "Hardware"
end tell
end tell
close the first window
end tell


That should do. I've got no single CPU MDD to test this on. Seems like the preference panel isn't rightly indicating how many CPUs are in use. When I select single CPU mode, the next time I bring up the panel it shows dual mode again. You say you can tell by whether the machine eventually crashes. If so, post. Good luck.



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: trevbucky on Nov 18, '07 05:44:43AM

Are you saying that with Nap mode & selecting two processors, that it crashes Dual processor MDD Powermacs on 10.5? after how long?... because with Nap, mine doesnt crash on 10.4 with two 1 ghz processors! I wouldn't want to upgrade to 10.5 if that was the case.



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: theusjones on Nov 18, '07 12:48:20PM

Works perfectly well. I have a dual processor MDD, running Leopard, nap mode enabled, uptime three days including some real work.

The system temperature right now is 109.4F, instead of the 137F it would generally be without nap mode. No performance penalty, much quieter operation, less heat stress on the components, and wonder of wonders, I get to use the new Xcode. No regrets.

Here's what I make of the previous comment: I think the previous poster had a single processor machine, that the Hardware panel running under Leopard can't determine whether the machine is in dual or single processor mode so it leaves the dual processor mode radio button set by default when it opens, then when it closes it finds that radio button set, and so it sets dual processor mode, then that lead to weirdness on that person's single processor machine.

Long story short, the working theory is that if someone with a single processor machine uses the script given above which explicitly sets single processor mode, it ought to be fine.

Anyone with a single processor machine having weirdness ensure?



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: QJB on Aug 04, '09 02:29:38AM

What CPU (745x) and CPU version do you have? I got a machine running dual 7450 rev 2.1 without any trouble in NAP mode.

Not all 7450 models seem to support napping in dual CPU configuration though. Perhaps the reason Apple removed the feature in newer versions.



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: kaylan on Dec 08, '07 06:18:48AM

Thanks for the reply and apologies for the delay in responding. I will try new version of the script. I do indeed have a 2 x 1.4G MDD with a firewire 800 port in the back. If you look into xlr8yourmac.com, you will find that with tiger and even before, due to hardware issues, if you turned on nap mode in these machines, after a long while (typically days), they do crap out. Some people have reports suggesting that theirs are fine, however, they seem to be the minority, or they can not attribute the crashes to the nap mode. G5 machines did not have this issue. What I did find out, is that if I switch off one of the two CPUs that I have BEFORE enabling the nap mode, everything was fine. You had reverse the order by turn second cpu on when necessary AFTER disabling the nap mode. So I wrote scripts to do this, and automatically managed nap mode and cpu count based on load. Of course Leopard broke that. So now, using your original script, nap mode on and and forced on two cpu's, reliability goes (presumably) down the tube as that was exactly the condition with Tiger. This is also the reason why apple disabled the nap mode thing on these machines as I understand it, it is a hardware related issue, as on the single CPU machines, nap mode is on by default 24/7. I really do appreciate your providing an added script. Will test and report if positive results. Thanks.



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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: QJB on Aug 04, '09 02:51:41AM
Looking at this code from the FreeBSD project:
http://src.gnu-darwin.org/src/sys/powerpc/powerpc/cpu.c

Could a Mac developer use this code to build a small application? Or involves this a lot of work (building a KEXT?)?

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10.5: Enable nap mode in 10.5 on G4 MDD systems
Authored by: lopaka1998 on Apr 30, '11 11:42:51PM

Thanks for this. One minor modification:

put the tell command down a line and put this as the first command:

delay 3

This will give the script a 3 second delay in executing. The old script sometimes messed up as the chud program hadn't quite loaded yet when the script tried to execute. This is on a mdd dual g4 867Mhz. The 3 second delay should allow adequate time for chud to load and avoid this occasional error.

Peace!



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