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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > How hot does your quad-core iMac get?

How hot does your quad-core iMac get?
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Eug
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Dec 27, 2011, 06:37 PM
 
I'm wondering how hot your i5 or i7 iMac gets. In ambient room temp (19C 66F), if I'm running Handbrake (700%+ CPU usage, and even sometimes briefly over 790%), my 2.93 GHz i7 iMac gets hot enough that the top of the iMac is hot to the touch and I wouldn't want to keep my hand there for more than say 10 seconds because it feels too hot.

iStat Pro tells me the CPU is at 69C with fan around 1150 rpm (not really audible), or down to 60C with fan around 1860 rpm (audible). The GPU diode is 65-68C and the GPU heatsink is 62-64C. Power supply 2 is now up to 78C.

I see from this page that the maximum operating temperature is supposed to be 72.7 C. My temps are getting awfully close.

P.S. Even with 8 virtual cores, this machine may take 2 hours to transcode a 1080p movie with my current settings.
( Last edited by Eug; Dec 27, 2011 at 06:46 PM. )
     
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Dec 27, 2011, 07:59 PM
 
2 hours to transcode a 1080p video doesn't seem bad at all.

The i5 quads at my school get pretty hot up there, even with just basic stuff. When I use them for editing HD footage, it's just as you describe, almost too hot to touch. I'm not sure what the actual temps or fan RPMs are, but in the quiet of the library, I can hear the fan occasionally.
     
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Dec 27, 2011, 08:21 PM
 
About that hot.

Use faster encoding settings.
     
Eug  (op)
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Dec 27, 2011, 09:17 PM
 
Thanks for the input. So it's not just my iMac then.

About faster encoder settings, I am doing that for the time being. 1080p stresses out that AppleTV 2 I got for Xmas so I'm re-transcoding to 720p (which is OK since my projector is only 720p anyway).

However, I personally would have waited until AppleTV 3 came out with the A5 in it if I had made the purchase decision myself, but it was a gift.

     
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Dec 28, 2011, 07:57 AM
 
Are you concerned that your CPU is getting too hot, Eug? If so, I'll tell you that even going well into the 70C range isn't too hot for it. You don't want to run it that hot constantly, but that's still a pretty comfortable distance from the top heat levels at which it would become dangerous to run.

"The natural progress of things is for liberty to yield and government to gain ground." TJ
     
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Dec 28, 2011, 11:36 AM
 
Originally Posted by Eug View Post
I'm wondering how hot your i5 or i7 iMac gets. In ambient room temp (19C 66F), if I'm running Handbrake (700%+ CPU usage, and even sometimes briefly over 790%), my 2.93 GHz i7 iMac gets hot enough that the top of the iMac is hot to the touch and I wouldn't want to keep my hand there for more than say 10 seconds because it feels too hot.

iStat Pro tells me the CPU is at 69C with fan around 1150 rpm (not really audible), or down to 60C with fan around 1860 rpm (audible). The GPU diode is 65-68C and the GPU heatsink is 62-64C. Power supply 2 is now up to 78C.

I see from this page that the maximum operating temperature is supposed to be 72.7 C. My temps are getting awfully close.

P.S. Even with 8 virtual cores, this machine may take 2 hours to transcode a 1080p movie with my current settings.
I wouldn't worry about CPU or GPU. 72.7 is the temperature at which the CPU starts to throttle if ran at 100%, ie drop clockspeed and start introducing NOPs to drop temperature. The temperature where it will force automatic shutdown is much higher (EDIT: 105C is shutdown) and even that won't damage the CPU (apparently 111C is when Lynnfield starts hurting). The GPU isn't even warm. The PSU is a bit hot, though - I've never seen mine that high - but that one has a fan all of its own, so it shouldn't be an issue. How fast does the PSU fan (the HD fan) spin when you do this?
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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Dec 28, 2011, 12:36 PM
 
Originally Posted by Eug View Post
About faster encoder settings, I am doing that for the time being. 1080p stresses out that AppleTV 2 I got for Xmas so I'm re-transcoding to 720p (which is OK since my projector is only 720p anyway).
I don't just mean dropping the resolution, I mean faster encoding settings (less analysis, etc). The HB nightlies have support for the x264 presets, use veryfast instead of normal. Although eventually you'll become decode bound with your HD source if they don't have multithreaded decoding for your source codec.
     
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Dec 28, 2011, 07:35 PM
 
Mine gets equally hot. The back is a giant heatsink, so it being hot is a very good thing. Reminds just how inefficient our electronics still are.
     
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Dec 28, 2011, 08:31 PM
 
I have to run a fan that blows over my Macbook Pro when playing SWTOR to keep the computer from locking up from over heating. If you are really concerned you can run a external fan that blows the computer it will help a lot. The Mac's cases are part of the cooling system which is why they get so hot. The entire body of the computer radiates heat out.
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Dec 29, 2011, 07:44 AM
 
Originally Posted by Athens View Post
I have to run a fan that blows over my Macbook Pro when playing SWTOR to keep the computer from locking up from over heating.
That's not good. I know that it can help to pin up the back of the Mac an inch or two to allow airflow under it, but you shouldn't have to use an external fan. Do you have one of the infamous nVidia GPUs? Did you mess with the fan system? You're right that the case is part of the cooling system, but that's not a reason for the computer to lock up. The fan should rev to compensate.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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Dec 29, 2011, 03:47 PM
 
Windows 7 + SWTOR at full quality minus the shaders and iTunes. I am pushing my 2008 MacBook pro way beyond its limits and after a hour or so it over heats. The fans just can't keep up with the CPU and GPU being maxed out for hours on end. I am just pushing my Mac extremely hard. It's also why I know a external fan can make a
Massive cooling difference.
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Dec 29, 2011, 04:04 PM
 
I know that I keep pushing this hint all over, but Have you tried vacuuming out your vents? It's mostly an issue on certain iMac G5 models, but depending on the environment, it can help on other machines as well.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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Dec 29, 2011, 04:18 PM
 
Um no you don't use a vacuum. You get a compressed can of air and follow instructions like not tipping it up side down for the first blast of air.

Vacuums + computers are bad except those small low powered portable ones designed for electronics.

That said the computer getting warm is normal. Nothing said so far makes me think there is any problem that needs to be addressed. I only suggested a external fan for peice of mind reasons.
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Dec 29, 2011, 05:08 PM
 
The vacuum won't do much harm from outside the case. That advice comes form the days we used to vacuum out our ATX cases.
I have plenty of more important things to do, if only I could bring myself to do them....
     
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Dec 30, 2011, 03:39 AM
 
Doesn't really get hot at all, just maybe warm from time to time depending on what I do to it. Probably built up dust in your computer man.
     
Eug  (op)
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Dec 30, 2011, 04:54 AM
 
Originally Posted by P View Post
I wouldn't worry about CPU or GPU. 72.7 is the temperature at which the CPU starts to throttle if ran at 100%, ie drop clockspeed and start introducing NOPs to drop temperature. The temperature where it will force automatic shutdown is much higher (EDIT: 105C is shutdown) and even that won't damage the CPU (apparently 111C is when Lynnfield starts hurting). The GPU isn't even warm. The PSU is a bit hot, though - I've never seen mine that high - but that one has a fan all of its own, so it shouldn't be an issue. How fast does the PSU fan (the HD fan) spin when you do this?
The power supply just now was 74C and the fan was at 1800 rpm. The CPU right now is only about 60C, with the fan at just under 2000 rpm.

Originally Posted by mduell View Post
I don't just mean dropping the resolution, I mean faster encoding settings (less analysis, etc). The HB nightlies have support for the x264 presets, use veryfast instead of normal. Although eventually you'll become decode bound with your HD source if they don't have multithreaded decoding for your source codec.
I'm just using a modified AppleTV 2 preset, with b-adapt-2 and rc-lookahead=100, and RF = 17 (or sometimes around 18).

I don't like RF 19 at all for grainy material, but it's OK for smooth stuff like CG animation. RF 17 looked great with grainy material, but grain + RF 17 = huge file sizes.

BTW, I've since noticed that 1440x810 works well with Apple TV 2 if the file is a lower bit rate decode. However, with more complex stuff, I get occasional stutters. This stuttering increases dramatically at 1080p and is completely gone at 720p, and 720p with that setting gives me file sizes I can tolerate.
( Last edited by Eug; Dec 30, 2011 at 05:05 AM. )
     
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Dec 30, 2011, 12:13 PM
 
Originally Posted by Eug View Post
I'm just using a modified AppleTV 2 preset, with b-adapt-2 and rc-lookahead=100, and RF = 17 (or sometimes around 18).
rc-lookahead=100 is crazy and slow (and uses a lot of memory but that's not much of an issue these days). Even the x264 placebo preset only goes to 60. Are you having rc issues with the default (40)?

What's the point of 1440x810 when the ATV2 only outputs 1280x720?
     
Eug  (op)
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Dec 30, 2011, 07:53 PM
 
Originally Posted by mduell View Post
rc-lookahead=100 is crazy and slow (and uses a lot of memory but that's not much of an issue these days). Even the x264 placebo preset only goes to 60. Are you having rc issues with the default (40)?
Nah. I just chose that number at random. I'll probably reduce it back to 60.

What's the point of 1440x810 when the ATV2 only outputs 1280x720?
1440x810 sometimes looks better on some computer screens. However, for a lot of material the bitrate jumps enormously with that, so I think I'll just stick with 1280x720 anyway. That also happens to be exactly 1/4" the resolution of my iMac too.
     
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Dec 30, 2011, 08:55 PM
 
Originally Posted by Eug View Post
About faster encoder settings, I am doing that for the time being. 1080p stresses out that AppleTV 2 I got for Xmas so I'm re-transcoding to 720p (which is OK since my projector is only 720p anyway).
The tv 2 doesn't output to 1080p anyway, so there's no point.
     
Eug  (op)
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Dec 30, 2011, 09:24 PM
 
Originally Posted by imitchellg5 View Post
The tv 2 doesn't output to 1080p anyway, so there's no point.
The point is so that you don't have to re-encode things twice.

If I had the AppleTV 3 with full 1080p High Profile 4.1 support, I'd just encode everything at 1080p when possible, disk space be damned.
     
   
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