2017 iMac 5K - CPU Temp Diffs?

[HappyIntro]

I'm in the market for a 5K iMac, and I'm wondering about the different CPU options. I've heard that iMacs run hot, so would a faster CPU increase the heat output relative to the slower options, making it hotter?

I've read that the amount of heat that is emitted from the CPU is independent of the base clock, as long as all the CPUs have the same TDP. So can I assume that there will not be an increase in how hot my iMac runs regardless of which CPU I choose? (All other variables being the same - looking at 16GB/512SSD model). Any feedback appreciated.

 

[cynics]

In general when comparing the same generation and series CPUs (ex Skylake Core series) the faster they are the hotter they are capable of getting hotter.

If you aren’t doing anything that pushes the CPU temps wont vary as much. At idle they will be quite similar.

All the CPUs are capable of running hot (90+ Celsius) it’s just the higher end CPUs completely saturate the heat sink and run the fan faster (louder).

The current 2013 design appears to be specifically built around Haswell. Current high end intel CPUs aren’t getting cooler nor the the demands on the CPU lessening (4k video encoding). So we now have machines capable of running at temps that push throttling conditions.

Regardless get the machine your work load demands. I wouldn’t recommend “future proofing” an iMac with a high end CPU unless you specifically foresee a future need for it in your workload. I’m still using an iMac with a 4th gen i5 and only now after nearly 6 years do I see very mild bottlenecks when photo editing RAW. The main bottleneck is encoding HEVC video but that is due to the CPU not having native HEVC support, so I wouldn’t have been in a better situation with the i7 CPU from that year.

If you do do heavy CPU intensive task and noise is more of a concern then speed of task completion go for the i5 models. Referring back to my i5 even a video transcode that takes HOURS can’t fully saturate the heat sink so the fan won’t lift off its idle 1200 rpm so it’s nice and quiet. However the consequence is a transcode time that 1/3 longer than a faster noisier CPU.

Honestly I hate being forced to choose between fast and noisy or slow and quiet. The only choice should be fast and more expensive or slow and cheaper. I build Windows PCs and noise and temps are closely monitored during a 24 hour stress test. I would consider the way the higher end iMacs run as a problem and I would address it with better heat sinks, fans (more, better positioning, etc) but then again my machines don’t compete with aesthetics of an iMac.

Good luck!

 

[HappyIntro]

Thanks cynics for the great response, this is very helpful. I'd sacrifice some performance for a quieter iMac, so it looks like I'll take a pass on the i7. Of course I realize that there may be a spec upgrade coming soon, so I'm not sure how long I want to wait to order in the hopes of an impending upgrade that may make the cooling issue more critical (e.g., cramming hex-core cpu in current enclosure) or less (improved air-flow/cooling like the iMac Pro).

 

[cynics]

Thanks cynics for the great response, this is very helpful. I'd sacrifice some performance for a quieter iMac, so it looks like I'll take a pass on the i7. Of course I realize that there may be a spec upgrade coming soon, so I'm not sure how long I want to wait to order in the hopes of an impending upgrade that may make the cooling issue more critical (e.g., cramming hex-core cpu in current enclosure) or less (improved air-flow/cooling like the iMac Pro).

My advice only applies to the current 5k iMacs so watch reviews once a new model comes out because something may change.

I'm sure a lot of others with 5k iMacs will chime in since noise is a pretty big factor for many as well.

 

[SkiHound2]

I've done quite a bit of online searching about this. FWIW, I have no personal experience with the i7 version. The i7 version in the current iMacs is a 91 TDP processor and from all I read, the 580 GPU runs hotter than the other units as well. So the heat/fan noise issues seem to largely be related to that set up. That said, there seems to be quite a bit of disagreement about how universal and/or serious the issues are. Lots of users seem very happy with that set up. If you search for 2017 iMac heat and fan noise you'll get quite a bit of info. There's a long thread about this topic in the Mac forum on dpreview. One person posted a bunch of performance numbers under different loads and the 3.5 version seemed to be the sweet spot. The 3.8 i5 is also a high TDP chip seemed to throttle back a bit, so performance differences between it and the 3.5 were quite minimal. If you're using applications that make a lot of use of multi-threading the i7 will obviously be faster. I ordered a 3.5 version. It was quiet and seemed to run fast. I liked it. I was having weird problems with it stopping streaming of Youtube, Vimeo, and iTunes audio after a certain period of sleep. Apple tech support couldn't figure it out and I decided I need to return the machine in my 14 day window. I think it was software and not hardware but I wasn't keeping a machine that was not working properly when Apple tech couldn't come up with a solution. At this point I think I'm going to limp along with my old Mac Mini. I'm kind of hoping they offer the 8th generation i7 none k (the one that's a little lower and is a 65 watt chip) as an option in the next iMac. I think that would kind of be the sweet spot between performance and heat.

 

[oVerboost]

Also worth remembering that from all the millions of 5k iMac's sold, there's probably a very small amount with heat and noise issues which could be down to faulty hardware or software that's not optimised etc.

Have done 4k video editing, multi-layer photo editing and a bit of gaming, and not experienced any heat issues or noise at all from my 5k 2017 3.4 i5.

 

[HappyIntro]

Also worth remembering that from all the millions of 5k iMac's sold, there's probably a very small amount with heat and noise issues which could be down to faulty hardware or software that's not optimised etc.

Have done 4k video editing, multi-layer photo editing and a bit of gaming, and not experienced any heat issues or noise at all from my 5k 2017 3.4 i5.

That is good to know, thanks.

I've done quite a bit of online searching about this. FWIW, I have no personal experience with the i7 version. The i7 version in the current iMacs is a 91 TDP processor and from all I read, the 580 GPU runs hotter than the other units as well. So the heat/fan noise issues seem to largely be related to that set up. That said, there seems to be quite a bit of disagreement about how universal and/or serious the issues are. Lots of users seem very happy with that set up. If you search for 2017 iMac heat and fan noise you'll get quite a bit of info. There's a long thread about this topic in the Mac forum on dpreview. One person posted a bunch of performance numbers under different loads and the 3.5 version seemed to be the sweet spot. The 3.8 i5 is also a high TDP chip seemed to throttle back a bit, so performance differences between it and the 3.5 were quite minimal. If you're using applications that make a lot of use of multi-threading the i7 will obviously be faster. I ordered a 3.5 version. It was quiet and seemed to run fast. I liked it. I was having weird problems with it stopping streaming of Youtube, Vimeo, and iTunes audio after a certain period of sleep. Apple tech support couldn't figure it out and I decided I need to return the machine in my 14 day window. I think it was software and not hardware but I wasn't keeping a machine that was not working properly when Apple tech couldn't come up with a solution. At this point I think I'm going to limp along with my old Mac Mini. I'm kind of hoping they offer the 8th generation i7 none k (the one that's a little lower and is a 65 watt chip) as an option in the next iMac. I think that would kind of be the sweet spot between performance and heat.

Thanks for the tip about the dpreview thread on this topic. It's been awhile since I've visited that site; I'd forgotten how much good content is in their forums. I found the thread you mentioned and I'm working through it now.

 

[SkiHound2]

Well, I don't know about much good info on dpreview. Lots of fanboyism, and format and brand bashing. Much by folks that I doubt ever really do photography. But some of the non-brand forums like the computer forums, retouching forums, and forums about specific photography genres can be useful. I thought that thread was especially informative. With some searching you'll that a lot folks using them for music complain about the fan noise of the i7 variant. I really think that case does better with the lower power chips. The i5 3.4 and 3.5 are 65 watt chips and I don't see anyone complaining about excessive fan noise with those. I'd bet if you tried to crunch through some really cup extensive stuff the fans might rev up a bit. But it seems the fans on the i7 based models can get going with much lighter use. Just not enough cooling in those cases. That's why I'm hoping we see the lower wattage i7 in the next generation. Who knows when or if that might ever appear.