@Necere
Would you look over these notes & tell me if you think this would be feasible...?!?
2019 modular Mac Pro
7.7" cubed, but with the same vertical curved corners as the Mac mini (of which we are sharing the width & depth dimensions), appropriately sized feet to match the proportions of the chassis while still providing appropriate breathing room for bottom intake fan.
A quick video for insight into the PSU...
So, with that view of the layout on the Space Grey Mac mini, we move to the 7.7" Cube modular Mac Pro version...
Take the same PSU concept, make it go all the way up in the 7.7" tall (excluding feet) chassis. That should allow about 6x the volume for the PSU than in the mini. The mini PSU is 120W, hopefully Apple can do a 750W PSU...?
So now we have three of the 'interior walls' flat, but one still has those pesky curved corners (the one across from the PSU). What to do...? Storage...! Four 2.5" SSDs (two stacks of two SSDs) should not be an issue. That 'flattens out' the fourth 'interior wall'.
So on the inside of the front of the chassis, there will be a backplane with four daughtercard slots, all arraigned vertically.
First daughtercard next to the PSU is the main daughtercard, Threadripper 3 as outlined in above post, but only the two 180W versions (24C/48T & 32C/64T) with copper vapor chamber heatsink & four SO-DIMM slots (RAM slots located below PCH heat sink), & T2 chip with two (Apple-proprietary) NVMe SSDs; heatsink fins & RAM oriented vertically. Let's say the package 'stack' (daughtercard PCB / socket / CPU / vapor chamber heatsink) is 60mm thick, 140mm tall, & as wide as possible. Smaller copper vapor chamber heat sink on PCH as well. T2 / SSDs located on backside of PCB.
The next two daughtercard slots would be PCIe 4.0 x16 slots, for (Apple-proprietary) GPUs, more copper vapor chamber heat sinks with vertically oriented fins. Let's say these package 'stacks' are 30mm thick, with the heat sinks 140mm tall & as wide as possible.
GPU options (again, these are all going to be Apple-proprietary, not drop-in industry standard PCIe GPUs), all these have internal pass-thru (via the backplane) from GPU to rear TB3 / USB-C I/O.
Radeon RX 3090X (7nm Navi 20, 64CU , 16GB GDDR6, 225W, available Q1 2020)
Radeon RX 3080X (7nm Navi 10, 56CU , 8GB GDDR6, 190W)
Radeon RX 3070X (7nm Navi 10, 48CU , 8GB GDDR6, 160W)
Final daughtercard is the rear I/O card, this will be a 10mm thick package; four TB3 / USB-C ports, four USB-A ports, two 10Gb Ethernet ports, one 3.5mm headphone jack. If Apple has some nice ultra-high speed backplane action, this could allow I/O to be upgraded in the future!
Two Apple-specific (one can hope) Noctua Chromax NF-A14x25 PWM fans , one on the bottom as intake & the other on the top as exhaust. Fans 'smart-controlled' by inputs from a myriad of temp sensors.
So...! All that. packed into a 7.5 liter volume (not including feet).
Am I crazy, or might this be a viable SFF personal desktop workstation...?!?
Imagine what kind of Performance Per Liter score a 32C/64T CPU & two Radeon RX 3090X GPUs can achieve...!