MP All Models So long, old friend.

[mikas]

A driver stack for dGPU. Or at least allowing one for 3rd parties. It would keep the door open for xMax, and for a real Mac Pro. Or anything not possible at this point in time.

They (Apple) used to support intel iGPU and discreet AMD and NVIDIA GPU, and at the same time, in a professional laptop at least they did. Please do that again.

You can still keep your SoC GPU, it's pretty amazing for laptops, and even for some desktops I agree. But it's not everything you could hope for, nor is it the best there is for every use cases. So both of the best worlds, in one mean of a machine.

And this would mean a PCIe slot at the moment. Maybe an x16 dual slot and x4 for some edge uses.
And a free slot or two for 3rd party NVMe. Still can keep your own implementation of your T2 driven Flash Drive, or how ever you want to call it. Please make it so that Mac can operate from 3rd party NVMe too if it needs to do so.

Yes I know, I'm not a software specialist, maybe all this is unachievable, or it's too expensive or whatever. But that would convert me possibly back to Mac. Even with those horrible upsell prices of Apples.

I'm pretty sure they can do it if they want. It's just that at this time, they just earn too much from their business to even think about all of this random fuzz we sprout out in the air - we, the marginal people; former loud supporters, strong evangelists, power users, professionals, the think different crowd.

Now they want to sell us these one time use bricks. Just recently got one for the company; Mac Studio M4 Max 128GB/4TB, a hefty 5774€. Almost to the Max with M4. A M5 seems like becoming unobtainium soon here in north with these specs, so happy that we happened to get that at least. It's not in my use though, I am a PC guy now unfortunately.

Not sure if I'm onTopic anymore. Maybe I still am a little bit, mourning or something.

 

[escargot3]

Macintosh
PowerMac
Mac Pro

These are iconic and have a rich history in Apple folklore.

The iPhone maker doesn’t care for tradition, it wants an all-in-one machine to run the all-in-one app which is what the current macOS is. Apple Silicon architecture was designed to facilitate this.

Meanwhile there’s the sham of the 50th anniversary celebrations.

Macintosh
Quadra
Power Mac
Mac Pro
Mac mini
Mac Studio
27" iMac

Fixed that for you. These are the desktops that are iconic and have a rich history in Apple folklore.

Also Apple doesn't want an all in one machine as you say and have been extremely resistant to it as of late. Users have been begging for a revised 27" iMac or iMac Pro and they refused to do one. Instead opting for the modular option of Mac mini or Mac Studio paired with external monitor and peripherals (whether Studio Display or 3rd party).

 

[mode11]

Macintosh
Quadra
Power Mac
Mac Pro
Mac mini
Mac Studio
27" iMac

Fixed that for you. These are the desktops that are iconic and have a rich history in Apple folklore.

Stipulating desktops excludes the vast majority of Mac sales for the past few decades, as well as genuinely iconic designs such as the PowerBook Pismo, Titanium G4, Aluminium G4 (especially the 12"), MacBook Air and so on.

But focussing only on desktops, how can the iMac G3 not be considered iconic? Or iMac G4?? I agree the (later) PowerMac G3 / PowerMac G4 were great - with the smooth curves, looping handles and fold-down side, they offered something genuinely different. The 2013-on iMacs, including the 27", also reached a peak, with a design that smoothly blended to a narrow edge.

I'd dispute the Mac mini, though. Whilst it came into its element with the M4 redesign, for many years it was just the cheap Mac that Apple didn't really know what to do with. People always found uses for it, as you tend to with cheap but adequate computers (I used one for a bit as a server / HTPC), but I'd say it was functional rather than iconic. The Studio is in the same boat; I can see the appeal in terms of price / performance vs a MBP, but it's just a big lump of aluminium on your desk. If Apple changed the design, I doubt many people would miss (or remember) the old one. The Mac Pro 6,1, for all its faults, was a more iconic piece of design.

The tower Mac Pro is a funny one. I owned a 4,1 for many years and loved it for what it was - the only expandible Mac. The build quality was excellent. But like many people, I'd have jumped at a smaller 'xMac' with a single i7, a couple of hard drive bays, a single optical bay, and a few PCIe slots (i.e. the standard PC load out of the time). The G5's chassis was huge for the amount of expansion it offered, but Apple eventually made great use of all that space with the switch to Intel. It was a bit of a brick, and irrelevant to the mainstream Mac user, but I guess it could be considered iconic. The 2019 version probably had even less awareness with the general public, but Apple went all-out with the design, so it's hard not to consider that one iconic.

 

[Mac3Duser]

I think we can discuss the design.

Under my desk, I have a Mac Pro 7.1 and a Dell Precision 5820, and the Mac Pro is obviously more attractive, but it's also much larger and bulkier, whereas the 5820 is already quite large. The fundamental difference is that in a more compact space, I have four 3.5-inch hot-swap server bays, adaptable to 2.5-inch drives, and two of them have NVMe hot-swap bays. There's also a slim DVD drive bay and a 5.25-inch bay with four 2.5-inch hot-swap bays. So, on the front panel alone, there are eight SSD/HDD slots. The interior has fewer PCIe lanes than the Mac Pro, but still allows for two GPUs and other cards. It's an older machine that works very well as a server/workstation; it's not attractive inside or out, but it's very well designed. Apple has a habit of offering much more expensive machines with much higher quality materials, and much more aesthetically pleasing designs. And that's what I expect from them.

I support Apple Silicon; I'm not against it at all.

However, I also ask Apple not to deprive me of NVMe ports and NVMe drives on the market for booting. I also ask them to let me choose whether or not I need to use a GPU for calculations, in addition to Apple Silicon, etc.
I don't necessarily want all machines to become Mac minis.

But obviously, I love Apple for its designs, especially for macOS, of course (except for Tahoe).

But design shouldn't prevent me from functioning well, but rather help me function better. That's the principle of design: how, starting from a set of specifications with constraints, to ensure that I can use the object/tool/machine more effectively.

 

[theluggage]

I support Apple Silicon; I'm not against it at all.

However, I also ask Apple not to deprive me of NVMe ports and NVMe drives on the market for booting. I also ask them to let me choose whether or not I need to use a GPU for calculations, in addition to Apple Silicon, etc.
I don't necessarily want all machines to become Mac minis.

...but systems-on-a-chip integrated GPUs, NPUs and on-chip SSD controllers (sharing on-package unified RAM) and relying on Thunderbolt for other I/O are an integral part of the Apple Silicon architecture. The only Apple Silicon chips that have enough PCIe lanes to support substantial internal expansion are the top-end Ultra chips which have a "spare" SSD interface as a side effect of being two complete Max dies fused together... and we've yet to see whether that's going to be true of future "ultra" chips given that M5 Pro/Max uses a more modular system of fused-together dies.

Even the M2/M3 Ultra have pretty pathetic PCIe lanes/bandwidth compared to Xeon or AMD systems (including the 2019 Mac Pro). Apple aren't being mean with PCIe for the sake of it - they'd have to produce totally new PCIe-oriented SoC dies to provide that bandwidth, and with the relatively low volume of sales for a new Mac Pro those chips would cost a fortune.

AS is exceptional in tablets, laptops and small-form-factor desktops, and may find a role in those high-performance computing applications where unified memory works better than dGPUs with separate/limited VRAM. If you have a heavy, PCIe-driven workflow then Apple Silicon simply isn't the tool for the job. You can custom build an Intel or AMD system from huge range of standard components to fit your needs. Apple's potential market would be a small and rapidly vanishing niche of high-end users who are locked into some legacy MacOS app - and if we're talking ML and scientific computing that's increasingly rare, with Linux becoming more and more significant if you hate Windows.

...even when the 2019 Mac Pro launched, all of Apple's speed claims were vs. iMac/iMac Pro - far more powerful, specialised, PC hardware was already available.

I'd have jumped at a smaller 'xMac' with a single i7, a couple of hard drive bays, a single optical bay, and a few PCIe slots

That would have been a great option at the time - and the Hackintosh community had already done all of Apple's R&D for them. At that infamous 2017 press conference (which, I suspect, was due to a bunch of key customers & developers being shown the iMac Pro prototype under NDA and laughing it off the stage) instead of hand-wavy promises of a new Mac Pro which turned out to be 2-3 years in the making, they could have picked up the phone to Foxconn and had a few container loads of officially Hackintoshes on the next boat from China.

However, that possibility ended with Apple Silicon, and considering how that has galvaniszed the rest of the Mac range, the Mac Pro was probably a fair price to pay.

The 2019 version probably had even less awareness with the general public, but Apple went all-out with the design, so it's hard not to consider that one iconic.

YMMV.
The Tesla Cybertruck is iconic, too.
The 2019 Mac Pro doesn't quite deserve that, but I think it was over engineered and an example of form-over-function rather than attention to detail. The entry-level model priced-out people just looking for a moderately powerful, expandable desktop Mac, even though the base specs were woeful and a substantially cheaper top-end iMac could be faster (and threw in a 5k display). If you needed the expansion potential and were going to fill it with $10k+ of extra hardware it started to make sense - but that pushed it into a specialist market where it was up against the huge customisability of PC hardware. Relying on users with legacy MacOS-dependent workflows is not a long-term plan.

 

[mode11]

which, I suspect, was due to a bunch of key customers & developers being shown the iMac Pro prototype under NDA and laughing it off the stage

Hadn't thought of that, but sounds quite plausible.

The 2019 Mac Pro doesn't quite deserve that, but I think it was over engineered and an example of form-over-function rather than attention to detail.

The 6,1 and 7,1 are both examples of Apple taking the opportunity to over engineer the Mac Pro. It's like they can only bring themselves to bother if there's the possibility of a design award. The 6,1 was straight up nonsense (though a nice collector's item now they're cheap), but the 7,1 at least had lots of room for expansion and was reportedly very quiet.

The MPX slots were an indulgence, though, given they add to the pile of single-generation, proprietary interfaces that pointlessly reinvent the wheel. Providing triple 8-pin headers next to the main x16 slots (or heck, even a proprietary high power header you could buy adapter cables for) would have been sufficient. And I don't know how useful being able to route video to any TB port really is in practice - don't people just plug monitors into video cards?

I guess the bottom line is that the 7,1 case was nice, but its CNC-heavy design made it needlessly expensive. And 'fundamentally rethinking' the tower was something no-one asked for, yet forced people to wait 2-3 years. By which time customers had just enough time to sink $10K+ into it, before the announcement of an architecture transition.

 

[Basic75]

A driver stack for dGPU. Or at least allowing one for 3rd parties. It would keep the door open for xMax, and for a real Mac Pro. Or anything not possible at this point in time.

I don't expect this to ever happen. What I do expect to happen is for Apple to use the opportunity of only having to support Apple Silicon where CPU and GPU are cache coherent and have shared page tables to simplify macOS a lot by finally being able to assume such a closely coupled GPU instead of having to check for separate "VRAM" on a dGPU all the time.

 

[Mac3Duser]

You all know that tinyGPU exists ?

 

[theluggage]

Hadn't thought of that, but sounds quite plausible.

It's just speculation - although I think its evident that some sort of pushback from key players over the lack of "modular" Macs prompted that press conference. It's pretty clear that they had no concrete plans for a new Mac Pro at that point. However the iMac Pro must have been in active development at that point (love it or hate it, the released product didn't look like a last-minute kludge) and may have been ready for the more strategically important partners to get a sneak peek. At that point, the Trashcan was long overdue for replacement, the Mini seemed to have been left to wither, too - the iMac seemed to be the flavour of the month for the desktop.

And I don't know how useful being able to route video to any TB port really is in practice - don't people just plug monitors into video cards?

Well, TB host ports are supposed to offer video - and since the MP didn't have an integrated GPU at the time, video for the onboard TB ports had to come from a GPU card. TB interface cards for PCs came with a fugly external cable to connect to the video out, so MPX was an improvement over that. The default GPU needed thst... but then all of the "upgrade" GPUs had extra TB ports on the card (and the base model GPU was straight-to-landfill anyway) so, go figure...

I don't see MPX itself as a problem, since it was fully backward compatible with regular PCIe and did reduce the amount of knitting. If the Mac Pro line had continued then it may have got established, but...

By which time customers had just enough time to sink $10K+ into it, before the announcement of an architecture transition.

...so Apple should have known well in advance that MPX - if not the whole 2019 Mac Pro - was going to be "one and done". Which is frustrating.

 

[zephonic]

You all know that tinyGPU exists ?

I saw the Ziskind vid, but got the impression it mostly works for compute, for graphics not so much?

However, I also ask Apple not to deprive me of NVMe ports and NVMe drives on the market for booting. I also ask them to let me choose whether or not I need to use a GPU for calculations, in addition to Apple Silicon, etc.
I don't necessarily want all machines to become Mac minis.

I feel like a Mac Studio with two or four user-accessible M2 slots would satisfy a large segment of the Mac Pro user base. I would conceivably trade in my MBP M1Max for that.

But obviously, I love Apple for its designs, especially for macOS, of course (except for Tahoe).

To me Tahoe has a lot of Lion vibes.

 

[Basic75]

You all know that tinyGPU exists ?

But it doesn't integrate the GPU into the system and doesn't do graphics, it just allows specialized applications to use them for compute kernels? Better than nothing, but no change to the big picture.

 

[SDAVE]

You all know that tinyGPU exists ?

Compute only bud. No video output. Doesn't help gaming or 3d acceleration at all.

 

[mode11]

To me Tahoe has a lot of Lion vibes.

Or iOS 7 vibes - a radical visual overhaul that was later dialled back.

 

[mode11]

It's just speculation - although I think its evident that some sort of pushback from key players over the lack of "modular" Macs prompted that press conference.

I'd always assumed it was the heat they were getting for the 2016-on MBPs that made them reconsider, but a poor insider response to the iMac Pro makes a lot more sense (being a desktop).

It's pretty clear that they had no concrete plans for a new Mac Pro at that point.

100%. The messaging implied they had chosen to 'share news' of a Mac Pro already in active development. But it was obvious they had decided to change course that morning, realised it would take years to get a new MP to market, and knew they couldn't maintain radio silence that long. Their MP customers would all be on Windows by then. So, loathe as they were to do so, they took the (hitherto unheard of) decision to be 'open'. Hand-picking a small number of tame journalists, inviting them to speak with senior leadership at Apple HQ, and relying on them not to ask any difficult questions.

However the iMac Pro must have been in active development at that point (love it or hate it, the released product didn't look like a last-minute kludge) and may have been ready for the more strategically important partners to get a sneak peek. At that point, the Trashcan was long overdue for replacement, the Mini seemed to have been left to wither, too - the iMac seemed to be the flavour of the month for the desktop.

By the 5,1, the Mac Pro was likely struggling to justify itself to Apple beancounters (including beancounter-in-chief, Cook). The 6,1 was clearly intended to radically cost-reduce the Mac Pro line, making it vastly smaller and lighter for inventory and shipping purposes, whilst reducing config options. When it turned out to be an expensive flop, they sat on their hands for a while, recouping their investment, whilst umming and ahing about whether to discontinue the line entirely. They eventually had the bright idea to just create a 'super iMac' - adding a Xeon, a better cooling system and dipping it in Space Grey (it was no less upgradeable than the 6,1, albeit with less convenience). It likely felt like the obvious solution, until they showed it to stakeholders, who were underwhelmed. At which point they realised they needed to try harder.

Well, TB host ports are supposed to offer video - and since the MP didn't have an integrated GPU at the time, video for the onboard TB ports had to come from a GPU card. TB interface cards for PCs came with a fugly external cable to connect to the video out, so MPX was an improvement over that. The default GPU needed thst... but then all of the "upgrade" GPUs had extra TB ports on the card (and the base model GPU was straight-to-landfill anyway) so, go figure...

I don't see MPX itself as a problem, since it was fully backward compatible with regular PCIe and did reduce the amount of knitting. If the Mac Pro line had continued then it may have got established, but...

The MPX slots were neat, though given the GPUs were proprietary, passively cooled designs anyway, they could have included an internal TB connectors to connect to equivalents on the motherboard. Given corporate customers would configure them from factory and never upgrade them, no one would see the horror of a short, black internal cable. Private buyers / freelancers might order the base 580X, bin it, and fit an aftermarket RX6900XT that lacks MPX anyway.

...so Apple should have known well in advance that MPX - if not the whole 2019 Mac Pro - was going to be "one and done". Which is frustrating.

Of course. The plans for an architectural transition would be years in the making. They'd have known for a year or two before release that the 2019 would be a one and done, alongside concepts like PCIe GPUs.

 

[Mac3Duser]

The 6.1 design is absolutely wonderful... for Apple Silicon, and it would be wonderful that the Apple Silicon Mac Pro (or Mac Studio, or whatever you want to call it) adopted this absolutely legendary design.
If you opened it up, what would you find? Classic NVMe ports, yes indeed. The large central cooling system would be more than enough for an MX Max.
The I/O board? Thunderbolt, SD, microSD, HDMI, RJ45, and USB-A outputs (let's get crazy). Pure bliss.
In terms of design: exceptional.

And alongside this compact Mac Pro, we could have a Mac Pro SFF mini-tower with LP card slots, as I mentioned earlier, inspired by the MS-02 Ultra but with Apple's design, PCIe for processing (thanks, TinyGrad), additional cards, and a bit more power.

- Mac Mini (Mx or Mx Pro)
- Cylinder Mac Pro, now the "Mac Studio"? Yes, why not (Mx Max)
- Mini-tower Mac Pro (Mx Ultra)

And for imacs :
- iMac (Mx)
- iMac Pro (Mx Pro)

 

[theluggage]

I saw the Ziskind vid, but got the impression it mostly works for compute, for graphics not so much?

...compute (particularly on NVIDA) is a large part of what people are actually asking for these days & where Apple Silicon can fall short (if the workflow doesn't gain advantages from unified RAM).

Doesn't help gaming or 3d acceleration at all.

Apple do have a major gaming platform - its called the iPhone and doesn't take external GPUs.

The Mac is not, has never been and probably never will be a platform of choice for serious gamers. Even the GPU choice on the 2019 MP was dominated by "workstation class" GPUs which weren't really intended for gaming (I mean they may have been great - but not at the price).

I feel like a Mac Studio with two or four user-accessible M2 slots would satisfy a large segment of the Mac Pro user base. I would conceivably trade in my MBP M1Max for that.

That sounds great, but there is a problem: only the Ultra chips provide enough PCIe lanes to drive multiple x4 NVMe slots at respectable speeds.

Since the Mini and Studio do now use removable (but proprietary) flash modules for their SSDs. These are even user-replaceable (see the service manuals) but Apple will only sell you replacements, not upgrades. Third party upgrades already exist on a small scale - for people who are prepared to cross their fingers, buy from "some guy on the web" & have a second Mac to run the configurator software - so the hardware clearly isn't problematic. However, these won't be suitable "for the masses" or offered by well-known suppliers unless and until Apple properly supports third party upgrades and provides a better way of "bootstrapping" blank SSDs.

It's entirely within Apple's gift to offer a dealer-fit SSD upgrade path in the future, for people who've had to compromise on SSD capacity because of the current shortage. They did offer uprades for the Mac Pro (albeit at their usual sky-high prices).

 

[theluggage]

The 6.1 design is absolutely wonderful... for Apple Silicon, and it would be wonderful that the Apple Silicon Mac Pro (or Mac Studio, or whatever you want to call it) adopted this absolutely legendary design.

Nope.

The 6.1 design assumed that the heat output would be spread fairly evenly between one CPU and two medium-powered GPUs, and that these would each be on their own PCB. Hence the triangular "chimney" design. Even Apple admitted that this was a mistake which "painted them into a thermal corner".

You've seen the size of the logic boards in the Mini and Studio - they're smaller than any one of the 3 boards in a 6.1 and most of the heat comes from the single SoC package sitting underneath a big block of aluminium or copper. If the M5 Max/Ultra need more cooling they can just make it half an inch taller. The 6.1 design is totally irrelevant to Apple Silicon.

If you opened it up, what would you find? Classic NVMe ports, yes indeed.

The same arguments against NVMe ports in the Studio would apply to a trashcan (A: Less efficient having controllers on the module, B: Only the super-expensive Ultra SoC has the PCIe bandwidth and C: Apple prefers not to because $$$.)

The I/O board? Thunderbolt, SD, microSD, HDMI, RJ45, and USB-A outputs (let's get crazy). Pure bliss.
In terms of design: exceptional.

...all of which are already present and correct on the Mac Studio - which I don't have to rotate (straining all the cables) to get at the SD slot or front USB.

The Studio also fits nicely under my monitors, with the front ports accessible, occupying a bit of otherwise-dead desk space & can stack with hubs, storage etc.

 

[theluggage]

The Studio is in the same boat; I can see the appeal in terms of price / performance vs a MBP, but it's just a big lump of aluminium on your desk.

...and that is a problem because...?

Form follows function - and the function of a desktop PC is to power the components, keep them cool & keep your fingers away from the delicate bits. A big lump of aluminium is the tool for the job.

 

[mode11]

You've seen the size of the logic boards in the Mini and Studio - they're smaller than any one of the 3 boards in a 6.1 and most of the heat comes from the single SoC package sitting underneath a big block of aluminium or copper. If the M5 Max/Ultra need more cooling they can just make it half an inch taller. The 6.1 design is totally irrelevant to Apple Silicon.

To be fair, if Apple were re-using the 6,1 design for a Studio, they would redesign the heatsink. It would likely be a finned extrusion with an overall circular cross-section, flattened on one side to mount the PCB.

 

[mode11]

...and that is a problem because...?

Form follows function - and the function of a desktop PC is to power the components, keep them cool & keep your fingers away from the delicate bits. A big lump of aluminium is the tool for the job.

Yeah, but doesn't make for an 'iconic' design.

 

[SDAVE]

Apple do have a major gaming platform - its called the iPhone and doesn't take external GPUs.

The Mac is not, has never been and probably never will be a platform of choice for serious gamers. Even the GPU choice on the 2019 MP was dominated by "workstation class" GPUs which weren't really intended for gaming (I mean they may have been great - but not at the price).

Mobile gaming ≠ actual gaming.

I have a 6900XT (consumer card) in this 7,1 and can put a 5090 (consumer card), what do you mean it's not a "serious" gaming rig?

Apple always used to advertise gaming, if you remember Marathon and Quake days. It just falls flat after a minute because no developer wants to port things over.

 

[mBox]

But obviously, I love Apple for its designs, especially for macOS, of course (except for Tahoe).

Biggest PITA at work. This update(s) is constantly killing our network cred connections. I am sticking to Sonoma on my Mac Pro's, but laptop and others are dealing with the mess.

 

[theluggage]

Mobile gaming ≠ actual gaming.

For most customers, actual gaming = PC or console.

I have a 6900XT (consumer card) in this 7,1 and can put a 5090 (consumer card), what do you mean it's not a "serious" gaming rig?

It's not serious because you could have plugged the same GPU into a PC tower costing a fraction of the price of the base 7,1 and got the same, if not better, gaming performance.

If you've got a 6-year old MP that you're using for gaming that's great - but it doesn't mean there's an untapped market out there of people who would buy a brand new PCIe Mac Pro with "gaming" as a major justification.

Apple always used to advertise gaming, if you remember Marathon and Quake days.

Yes - and I've happily played things like Half Life and Portal natively on Mac, others in bootcamp or under parallels - without needing to plug in a "serious gaming" GPU. Apple Silicon Macs run Minecraft perfectly well. Some games on Steam are available for Mac. Lots of videos online of people running PC games at playable frame-rates under Parallels on Apple Silicon Macs, with integrated GPUs. Some work, others don't.

There's a big difference between "You can play selected games on a Mac if you want" - which is true even with Apple Silicon integrated graphics - and "Mac is a serious gaming platform".

 

[SDAVE]

For most customers, actual gaming = PC or console.

It's not serious because you could have plugged the same GPU into a PC tower costing a fraction of the price of the base 7,1 and got the same, if not better, gaming performance.

If you've got a 6-year old MP that you're using for gaming that's great - but it doesn't mean there's an untapped market out there of people who would buy a brand new PCIe Mac Pro with "gaming" as a major justification.


Yes - and I've happily played things like Half Life and Portal natively on Mac, others in bootcamp or under parallels - without needing to plug in a "serious gaming" GPU. Apple Silicon Macs run Minecraft perfectly well. Some games on Steam are available for Mac. Lots of videos online of people running PC games at playable frame-rates under Parallels on Apple Silicon Macs, with integrated GPUs. Some work, others don't.

There's a big difference between "You can play selected games on a Mac if you want" - which is true even with Apple Silicon integrated graphics - and "Mac is a serious gaming platform".

You're going in circles here. No one buys Macs for gaming in general but you're saying you can't seriously play games on them which is false. Especially on a Mac Pro which you can use a console gpu and boot into windows. I've been doing that since 2006.

With Apple Silicon there's a decent amount of native games like Death Stranding, Resident Evil series and so on that run natively. Plays fine.

 

[PaulD-UK]

@theluggage "At that infamous 2017 press conference (which, I suspect, was due to a bunch of key customers & developers being shown the iMac Pro prototype under NDA and laughing it off the stage)..."

@mode11 "I'd always assumed it was the heat they were getting for the 2016-on MBPs that made them reconsider, but a poor insider response to the iMac Pro makes a lot more sense (being a desktop)."

Both of the above, I think. Especially Intel's SkyLake/Kaby Lake development problems.
That was an inflexion point, and led to a reassessment of the potential of Apple’s iPhone SoCs being developed for MacOS use.

What with Apple having a senior management focussed on getting the production logistics right for shipping tens of millions of things, then finding that both their main future non-iOS products had serious design flaws....

The trash-can Mac Pro was entirely a Steve/Jony era concept, and Cook knew he had to come up with something forward-looking for the future. A strategy of 'consultation with Media Production industry experts' had helped save Apple in earlier eras...

The Mac Pro 7.1 plan was a mis-step, but an understandable one, given that the viability of a rebirth of the MacBook Pro line with Apple Silicon had yet to be determined.

Johny Srouji demonstrating the first AS prototypes must have made it clear to Apple's leadership where their future lay - and it wasn't with the 2019 Mac Pro...