[dijit]

The biggest issue was actually that the Mac Pro was designed specifically for dual GPUs- in the era of SLI this made some sense, but once that technology was abandoned it was a technological dead-end.

If you take one apart you'll see why, it's not the case that you could have ever swapped around the components to make it dual-CPU instead; it really was "dual GPU or bust".

Somewhat ironically, in todays ML ecosystem, that architecture would probably do great. Though I doubt it could possibly do better than what the M-series is doing by itself using unified memory.

[SpecialistK]

I'll admit that while I've used the trash can but never taken it apart myself. But I can't imagine it would have been impossible to throw 2x Polaris 10 GPUs on the daughterboards in place of the FirePros.

[dijit]

I think on a technical level you're right, but you need to run two of them and they'd need a custom design like so:

https://i.ebayimg.com/images/g/RQIAAOSwxKFoTHe3/s-l1200.jpg

For what is essentially a dead-end technology, I'm somewhat doubtful people would have bought it (since the second GPU is going to be idle and add to the cost massively).

the CPU being upgraded would have been much easier though I think.

[SpecialistK]

That's the crux, I think.

Apple even in 2017 had the money and engineering resources to update or replace their flagship computer - whether with a small update to Skylake & Polaris and/or a return to a cheesegrater design as they did in 2019.

But they chose not to. They let their flagship computer rot for over 2000 days.