I do remenber two year ago I calculated a possible thermal core for an hypothetical 750W tcMP (Xeon E5v4 + dual Polaris GPU), just switching to copper and a faster fan where enough, of course a TC in copper will be really expensive, a more conservative solution would be thermal pipes + aluminum fins, so the arguments from Apple about the thermal corner in the tcMP where BS, I believe simple they decided to wait until AMD got ready Epyc CPUs or there where really big issues with desktop development oversight.
There are also alternatives to copper as Aluminum-carbon nanotube constructs, exotic but seems a sound alternative, notwithstanding I believe the mMP will use std 2-phase heat pipe cooling .
I never looked at the heat saturation characteristics, but I am in agreement with you over many of the details. One thing I wanted to reply was that manufacturing has a large scale impact on the price. For example, $2 item in manufacture is valued at $200 in assembly situation and $250-$300 in a white box on its own. Another example, HP makes optical fiber routers for about $12 with lifetime warranty and the installer wants $500 for this item on a payment agreement.
My point is, the cost of any specific material is not so special. We are talking about a few dollars in reality. Where companies "lose money" is they sometimes have to include specific objects in a build "at cost price" just to make the retail budget work. That is why I called the Mac Pro the "Veyron of computing" because the build cost is possibly "too close" to the actual retail price.
Overall, my other comment is the lack of air turbulence in the central thermal core and the lack of heat transfer surface area are the main issue. Possibly the dimensions are too tight to allow for the necessary thermal mass. But then you pointed out a good solution and it makes sense. Why not.
Even the current Mac Pro can be "helped" with an air spreader directly inside the empty core. You cant get cooling from air travelling in the middle of the channel.
A design option for the team is also to run good GPU at a lower speed but include 3 GPU. Underclocking is not the end of the world and I can already hear people punching their stress ball just reading this. Underclocking is one of the forgotten tricks in modern computing. For this reason they include speed throttle in CPU design to allow the CPU to control the speed.
As we push slowly towards CPU / GPU shared processing, the number of possible CPU and GPU will only increase.
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