iMac 2020 is 100% Throttled

[riggieri]

Hey All

I am replacing a iMac Pro 8 Core/Vega56 with a 2020 iMac 10core/5700xt. It is faster really on all fronts, but I found out something that is very interesting and I have not seen it up in any benchmarks or reviews.

If you run a graphics heavy benchmark, like Unique Heaven and max the GPU out to 100% and then try to run the CPU at 100% using Cinebench, the system throttles itself, which makes sense, it does not have the cooling or power capacity to run both at the same time.

Cinebench With only CPU: 5579
CPU pulls 150W, tapers off to 110-30W
Cinebench while GPU is at 100%: 4159
CPU is throttled to 70-80W. With clock as low as 3.1GHZ, which is under base clock.
I tested this on the iMac Pro. Both GPU/CPU can pull all the watts they need at anytime.

Now, I'm not disappointed, because the system is just as fast as my iMac Pro if not slightly faster at all out rendering in Resolve. 80% faster in noise reduction. I understood the limitations, but damn Apple really should have put the iMac Pro cooling system in this. But we would have lost removable RAM.

 

[casperes1996]

100% utilization of both GPU and CPU basically never ever happens in real life workloads though. At most like 100/80. At least for extended periods of time. But yeah, happy you post this so that people know it’s a thing - people should know. But 100% workload on both is an unusual situation so I understand the engineering of the cooling system hasn’t taken it into consideration. - I only opted for the 8-core with 5700XT since I figured that with the cooling and whatnot the two extra cores likely wouldn’t help much, really, but in no real usage have I ever seen clocks below base, and in fact always a fair bit above - and that includes GPU+CPU