I hope from those it is clear that the PC has a LOT more volume in it than the Apple computer does.
I have been building my own PCs since the turn of the millennium and I can say the one thing I learned to keep an eye on was heat dissipation. For a PC this usually meant a lot of fans and perhaps liquid cooling solutions (there are even more crazy options than that).
I can also say that in my relatively small room where my computer is the computer noticeably heats the room (not sure but something like an 11’x12’ room). When pushing the limits of the PC via video editing or gaming I can hear the fans work harder.
So, how can Apple dissipate the heat generated from top-end computing (e.g. video work or gaming) without moving high volumes of air or using liquid cooling?
My only guess is the CPU and GPU throttle themselves but this would make their performance crap for power users (they are fine for surfing the web and doing email but then why spend that much money for one?).
I haven’t seen a teardown of the new iMac Pro, but here’s the guide to replacing the heatsink on the 27" iMac. As you can see, it has a custom-designed heat sink & heat pipe assembly connected to a centrifugal fan (“squirrel cage” fan). It’s all the same technology used on Windows systems, except these parts are all custom-designed to fit together in a very thin, flat package. Or you can think of it as a larger version of a typical laptop design, which has the same constraints.
Desktop/tower Windows PCs have very different design goals. They are designed to be standardized, modular, and easily customizable & upgradable.
While they do seem to have increased the cooling capacity the main limiter Apple faces with cooling is various international regulations of safe touch temperatures. As they use Aluminum cases which has a high thermal transmission rate they will do everything possible to keep external case temperatures below 60C.
While I am hopeful that, due to the negative press around the Mac Pro and the newer CPUs decreased power draw it will thermally throttle when it thinks that the temperature is approaching that threshold.
A smaller volume of faster moving air is less effective than a slower high volume of air and due to the design language and customer expectations they really have little option but to throttle. They need to work around the design language and the need for a relativity quite system so Apple tends to optimize for brief periods of high utilization at the cost of sustained performance.
Eventually the goal is to heat a volume of air with the energy your computer is dissipating. How you get the energy into the air is the only problem. Water cooling is just a way of moving the energy from the CPU package to the heatsink so that you can mount the heatsink somewhere convenient. Unless the heatsink is dissipating the energy no amount of water circulation will cool the CPU. Where you do gain is that the water reduces the thermal resistance near the CPU. But a heatsink mounted on the CPU can do this just as well. The trouble is that most motherboards are not designed to allow useful airflow over them. They are designed to fit into legacy formfactor boxes, boxes that have an uncontrolled amount of cruft filling them up, with cables and other junk in the air pathways, and no chance of optimising the airflow.
OTOH, if you are a computer manufacturer that has total control of the layout of every component, and has access to CFD analysis for the entire design, plus the design of the fans, airways, and the ability to integrate the entire thermal control system software with the design, you can do vastly better. It isn’t just the iMac where you see this. Have a look inside any high end 1U server. You see bespoke heatsinks, custom layout of the motherboard to use these heatsinks and air paths, and board layout that fits exactly with the airflow cooling all the supporting components.
Basically conventional motherboards in conventional cases are badly hamstrung by history. If someone was able to define and have adopted a modern case design, one that motherboard manufacturers could believe would be worth their while supporting, you could see much the same design as you see in the iMac or servers. But the market is geared towards custom boxes with LED displays, custom cosmetics, and a geek culture that values such sillyness as water cooling.
In high end computing water cooling is avoided desperately. It adds significant cost and maintenance headaches. You will find that vast majority of (if not all) supercomputers in the top 500 are air cooled.
Small format computers from all manufactures just throttle faster, With a 135W TPD CPU and a 225 W GPU there is nowhere close to enough plenum space for continuous use on the new iMac Pro.
While it used an older, larger feature size CPU I have empirical data showing that the trashcan Mac Pro would start to throttle after 96 seconds of continuous, integer CPU utilization.
It is not a use case of good or bad, but just different. But the iMac Pro is not the system those of use who have to maintain huge compile farms was looking for.
While there will absolutely be a user base that gains improvement from the changes none of the current lineup from Apple can support anything close to a 100% duty cycle without significant throttling.
I don’t think your point has been missed. The PC heatsink is a generic unit that must be able to work in a range of PC builds. The Mac heatsink only has to work in the build it was designed for and can be designed much more efficiently. Also PC users are accustomed to having big boxes under their desk, why bother designing an expensive, very streamlined, heatsink that 99% of users are just going to stick in a big roomy box?
As an individual who has been fighting the poor thermal performance of Apple based systems as a systems architect for a company that produces an software product and requires a compile farm; I have found zero evidence that Apple is some how providing superior thermal designs for high load use cases. To give a reference for scale and while I am not working with Amazon scale data centers we have approximately 350 Mac Pros and 485 quad core mac minis in the compile farm today.
In fact we had to use the Apple systems as our worst case estimation on developer productivity due to the issues surrounding their tendency to thermally throttle way below the hardware TPD (mostly due to the pain threshold limitations on cases as noted above)
Given the iMac Pro is vapourware, it is pretty hard to provide any real data. I am basing the potential on my experience with 1U servers in supercomputer applications. That tells me that Apple have the potential to provide a workable solution within the package. Whether they actually do or not we won’t know until the machine is released. I do agree that Apple have not been terribly good at meeting expectations for thermal management. OTOH, that is a design choice. They are not fools, they design what they think they will get away with. But I will contend that the average home PC solution is terrible. Things like water cooling and their ilk are just stone age solutions.
yes we will have to see, but the MacPro’s thermal design is far poorer than Dell, super-micro or Quanta 1U designs based on my empirical data. Really most of these calculations come down to the plenum size and can use HVAC calculations. As stated before the main advantages that many PC designs have is that they can throttle based on the package thermals, where recent laptop and apple desktop designs have to limit based on external case temperatures and human pain thresholds.
I am not exactly sure where water cooled or air cooled comes in, but the limiters in the apple product line are typically the plenum size and a choice to optimize for low noise. It does not make them a bad product but it does make it a poor choice if your need is for long duration high duty cycle operations.
That is an oversized aftermarket fan. It’s only for enthusiasts who want to make their PCs look impressive, or overclock the CPU and run it much faster than it was designed to.
but they don’t need to be that size. Those enormous, heat-pipe, multi-fan things are for enthusiasts and overclockers who want to keep their CPU as cool as possible. Apple (and other system integrators) merely need to keep temperatures within Intel’s stated limits.
