iMac Pro Fan Noise - difference between 8, 10, 14 and 18 cores?

Shadow Puppets

macrumors regular
Original poster
Nov 28, 2016
111
41
Helping a composer friend of mine pick an iMac Pro for use in his writing studio. It needs to be as silent as possible under load, but also be able to handle pretty mammoth Logic Pro X projects with a lot of plugins and software instruments. Think proper movie scores with full orchestras of software instruments.

I know that any of the computer's mentioned in the title would likely handle it all if we add enough ram, but we have two criteria:

- noise level under load
- future proofing

Would anyone be able to advise on fan noises across these machines, and whether the 18 core is likely to be louder, quieter, more regularly using the fans etc than the lesser core models?
 

SecuritySteve

macrumors 6502a
Jul 6, 2017
838
973
California
Hello, I have an 18 core model. When I ran my near-CPU pegging software (my own design for detecting vulnerabilities in software) I could run the iMac Pro for about half an hour before the fans turned on. Even then, they are relatively quiet. The real source of fan noise I've found is from games on the Vega GPU. I believe that if you really need the 18 cores, and can make use of them, they are worth it. The CPU is amazing, and will likely last for 4-5 years.

I cannot say the same about the GPU, but here's hoping there's a dual-channel eGPU solution to replace the internal GPU in a year or two.

Hope this helped.
 

Bryan Bowler

macrumors 68040
Sep 27, 2008
3,800
3,680
I cannot compare the fan-noise between the three models you mentioned, but I have the 18-core and lie Steve said, it is very, very silent. I am creative content creator and have only heard the fans a few times when I am well into a very long render, but the fan is barely audible to my ears. The other 96% of the time, I cannot hear the fans at all.

I suspect it might be hard to find someone that has directly compared the fan noise between the different iMac Pro models, but perhaps it has been done. Best of luck finding the data you're looking for!
 

richinaus

macrumors 65816
Oct 26, 2014
1,122
909
Wondered if there’s any more input on this? I appreciate the replies so far!
I have the 8 core and have similar results to the other guys here. Very quiet all the time and I have rarely heard the fans. I do lots of test rendering on designs all day on it, and I never hear it [in an office situation]. It can get quite hot on the back but still very quiet. It is an engineering marvel how they have done this. I have no idea how mine compares to others but it is certainly a great machine for my use and zero complaints.

I suggest you spec up the one you want and just order it from Apple, and see what happens when you load it up with everything. Apple will take it back no questions.
 

mpe

macrumors 6502
Sep 3, 2010
314
189
Same here. My 8core is completely silent no matter what I do with it (Xcode compilation, photo editing in Lightroom).

I almost never use the GPU though.
 

richinaus

macrumors 65816
Oct 26, 2014
1,122
909
Same here. My 8core is completely silent no matter what I do with it (Xcode compilation, photo editing in Lightroom).

I almost never use the GPU though.
I do use the GPU and have tested it in pure GPU rendering. It does kick in on these instances but is by no means offensive [and I am quite sensitive to fan noise]. Having said this given the OP use I doubt they will be hammering the GPU like this.
Just buy and test - there is no other way of knowing.
 

joema2

macrumors 68000
Sep 3, 2013
1,594
803
Wondered if there’s any more input on this? I appreciate the replies so far!
I have the 10 core Vega 64 version I used for large-scale documentary editing with FCPX. It is normally very quiet -- so quiet that I thought FCPX had crashed and wasn't running during some long renders and exports. Users who regularly push an i7 iMac become accustomed to the fan noise as a type of activity monitor -- the fan stops, you know the task is finished. The iMac Pro is mostly devoid of that feedback, so you must watch iStat Menus or Activity Monitor to know it's working.

However when pushed really hard I can infrequently hear the fans spin up. In a very few cases the noise is very noticeable. It's probably no louder than my 2017 i7 iMac but because the iMP is nearly silent most of the time, the difference is dramatic.

This graph from Mac Performance Guide shows the 18-core at full load pulls 256 watts vs the 10-core at 199 watts. Thermal output scales directly with this, so it implies the 18-core outputs 29% more heat at full load: https://macperformanceguide.com/iMacPro_2017-PowerDraw.html

Workload characteristics vary, so the only way to be sure is test it yourself. Unfortunately neither Apple's Joint Venture or Business teams have access to Configure To Order iMac Pros for professional testing. Your only choice is buy one, test it and return it if it doesn't meet your needs.

Because of this situation that forces you to buy a CTO iMac Pro for professional testing, you should only purchase it from a retailer that allows returns with no restocking fee. B&H and Adorama have a good supply of CTO iMac Pros, but they do not allow returns. For this reason it's probably better to buy it directly from Apple or a retailer that allows returns with no restocking fee.
 
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richinaus

macrumors 65816
Oct 26, 2014
1,122
909
I have the 10 core Vega 64 version I used for large-scale documentary editing with FCPX. It is normally very quiet -- so quiet that I thought FCPX had crashed and wasn't running during some long renders and exports. Users who regularly push an i7 iMac become accustomed to the fan noise as a type of activity monitor -- the fan stops, you know the task is finished. The iMac Pro is mostly devoid of that feedback, so you must watch iStat Menus or Activity Monitor to know it's working.

However when pushed really hard I can infrequently hear the fans spin up. In a very few cases the noise is very noticeable. It's probably no louder than my 2017 i7 iMac but because the iMP is nearly silent most of the time, the difference is dramatic.

This graph from Mac Performance Guide shows the 18-core at full load pulls 256 watts vs the 10-core at 199 watts. Thermal output scales directly with this, so it implies the 18-core outputs 29% more heat at full load: https://macperformanceguide.com/iMacPro_2017-PowerDraw.html

Workload characteristics vary, so the only way to be sure is test it yourself. Unfortunately neither Apple's Joint Venture or Business teams have access to Configure To Order iMac Pros for professional testing. Your only choice is buy one, test it and return it if it doesn't meet your needs.

Because of this situation that forces you to buy a CTO iMac Pro for professional testing, you should only purchase it from a retailer that allows returns with no restocking fee. B&H and Adorama have a good supply of CTO iMac Pros, but they do not allow returns. For this reason it's probably better to buy it directly from Apple or a retailer that allows returns with no restocking fee.
I agree 100% with the above. The iMac I7 fans would kick in all the time when pushed [I had a maxed 2017 model prior to the pro], whereas the pro is whisper quiet.
I bought the base model from Apple and returned it for a BTO with the Vega 64. There were no issues in doing this and Apple bent over backwards to help out. I have no qualms in saying this iMac pro is the best desktop I have ever worked on [this includes a lot of HP Z machines].
 
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