[iMac 27"] CPU Idle Usage 100% at all times

[Vortor]

Hi all,

Around May 2010, I ordered a 27" iMac (Mac OS X 10.6.8) with the following specs:

PROCESSOR 2.8GHZ QUAD-CORE INTEL CORE I7
MEMORY 4GB 1066MHZ DDR3 SDRAM - 2X2GB
HARD DRIVE 1TB SERIAL ATA DRIVE
GRAPHICS ATI RADEON HD 4850 512MB
OPTICAL DRIVE 8X DOUBLE-LAYER SUPERDRIVE
MOUSE APPLE MAGIC MOUSE-Z
APPLE SOFTWARE - IWORK NONE
APPLE SOFTWARE - FINAL CUT EXP NONE
APPLE SOFTWARE - APERTURE NONE
APPLE SOFTWARE - LOGIC EXPR NONE
APPLE SOFTWARE - FILEMAKER NONE
APPLE SOFTWARE - MS OFFICE NONE
APPLE KEYBOARD & USER'S GUIDE WL KYBD & USER'S GUIDE-PO
COUNTRY KIT COUNTRY KIT,IMAC 27-INCH-PRT

Until yesterday everything was running smoothly, but around midnight the electricity went out, came back for a split second and was gone again. After that, I took out the plug from the electrical outlet and went to sleep.

When I woke up this morning and turned on the computer, I noticed it took much longer than usual to boot. Also, it took a few additional minutes for the "I'm doing too many task at once" noise to go away.

Besides playing Starcraft 2 on low graphics, using a bit of Photoshop here and there, the occasional Screenflow high definition desktop recording and Premiere video editing, I don't do much cpu intensive tasks these days.

A user somewhere recommended to go to System Preferences > Startup Disk > Select Disk and click Restart. And it seems it solved the issue. At least, the boot is faster now. I decided to reset my PRAM and NVRAM. I'm not sure if it helped, but now the boot takes only around 30 seconds. I'm happy.

Still, my CPU idle usage is still at 90-100% all the time, even when I have no applications open? Is this normal?

I turned off Airport to see if the high % idle CPU usage would go down. No luck. After that, I checked Activity Monitor > All Processes. Everything seems fine, most of the values don't even reach 0.5% CPU usage. The top processes (usually Activity Monitor or Google Chrome) spike at 4-5% usage for a split second.

Maybe I'm overreacting, but I just want to be sure this couldn't cause some future problems, especially because the warranty is almost over.

Thanks for the help.

P.S: Not sure if it helps, but here's a screenshot from iStat Pro with only Google Chrome open.


Edit: Added screenshot.

 

[miles01110]

Launch Activity Monitor, select "All Processes", sort by CPU, and kill whatever is taking up so much CPU.

 

[Vortor]

I did that. The values are constantly changing, but most of the time the top processes that use more CPU are the Activity Monitor and Google Chrome with 0.8 - 3%.

iStat Pro still shows a constant 99-100% idle CPU usage. User, System and Nice stay at 0.

I did some research on the web. I don't know where it was but there was a person with same problem. One user said there could be a problem with the core.

 

[AdrianK]

It means your CPU is 100% idle. As confirmed by activity monitor. Idle is that state where the processor isn't doing anything.

 

[Bear]

I think we have a failure to understand terminology here.

If a system has "100% Idle" usage, that means it's idle, that is nothing is using the CPU.

 

[Vortor]

Oh crap, I feel embarrassed. Somehow my brain decided 100% idle cpu usage = 100% CPU usage. I just looked at "100%" and "CPU" and ignored the "idle".

The worst part is, the moment I read AdrianK's reply my second neuron started working and I immediately realized the stupid mistake I made.

Oh well, thanks anyway for the help.

 

[jwm2]

Mine is typically at 97-98% idle, even with several apps open and some widgets on my secondary screen. These iMacs seem to have plenty of processing power, i rarely see mine go above 20-30% under heavy loads.

 

[WilliamG]

At this point, get a UPS. I couldn't imagine running my iMac without one.