Apple very publicly acknowledged back before the current Mac Pro was released that they knew that a true pro model would need to be modular.
This does not rule out an SOC design. They could simply socket an SOC designed to support multiple sockets on one board.
If you want more CPU cores, a faster GPU or more memory, you would need to add a second SOC to the other socket or replace the entire chip, but at least it would still be possible to upgrade the system as a whole without replacing the chassis, power supply, and any other expansion cards/storage you might have within that case.
In April 2017, the one explicit use of "Modular" was in the exact same fashion it is used on the Studio. The display is modular.
" ...
As part of doing a new Mac Pro — it is, by definition, a modular system — we will be doing a pro display as well. ... We think it’s really important to create something great for our pro customers who want a Mac Pro modular system, and that’ll take longer than this year to do...
.... I think, as you talk about the pro user, the fact that our user base is split over notebooks, all-in-one desktops and modular desktops is important. ...
.... who use iMacs and who use Mac Pros, who use modular systems as well as all-in-one systems, who use the pro software we make. ... "
Transcript: Phil Schiller, Craig Federighi and John Ternus on the state of Apple's pro Macs | TechCrunch
You have already read the news. But we thought we would also use this opportunity to share a transcript of the interview with Phil Schiller, Senior Vicetechcrunch.com
Modular was consistently juxtaposed against the all-in-one iMac ( and iMac Pro which is heavily being hinted at in a couple of places in this transcript. This session wasn't solely about the Mac Pro... it is also basically an intro preparation for the iMac Pro (which was at that time a higher priority). )
Several aspects of the Mac Pro 2019 modularity that were pragmatically forced on Apple was that the Xeon W 3000 series was iGPU less. If pick that as a CPU then have to go to discrete GPUs. Apple had no choice. In 2020+ they do have choices because Intel is out of the primary SoC design choice position.
Same issue with RAM DIMMs. Basically an Intel driven design choice that Apple had to provision for.
As for GPUs...
" ...
We designed a system that we thought with the kind of GPUs that at the time we thought we needed, and that we thought we could well serve with a two GPU architecture… ..... But workloads didn’t materialize to fit that as broadly as we hoped.
Being able to put larger single GPUs required a different system architecture and more thermal capacity than that system was designed to accommodate. So it became fairly difficult to adjust. ..."
So they got on the large single GPU quest. Careful for what you wish for. Four Max sized dies 'glued together' on a single SoC is probably going to be one of the highest die space allocations for a single GPU that you can get in next year or so. Most of the Max die is the GPU and associated Memory and Video de/encode and display controllers. Four of them will be a large single GPU.
Getting apps to fully leverage the double and quad "Max like" GPU core clusters will probably 'materialize' better than the "two GPU , OpenCL workloads" did for the Mac Pro 2013 set up. Apple has a much more solid software foundation laid out at this point for that to happen on. And "unified memory" makes it easier to scale up once in the guidelines that Apple has laid down for the last several years. 12-18 months Apple allows 3rd party developers to optimize for their mega sized , single GPU then updated apps will probably turn in pretty decent performance.
Apple also said
"... We have a team working hard on it right now, and we want to architect it so that we can keep it fresh with regular improvements, and we’re committed to making it our highest-end, high throughput desktop system, designed for our demanding pro customers. ... "
Note that it is "we can keep it fresh". It isn't so the end users can keep it fresh by regularly ordering new parts from Frys/Newegg/Amazon/Microcenter/etc. It is so Apple can roll out updated product. ( and yes when they do that via modular means there is secondary fall out effect of the 3rd party stores being alternative options. But Apple isn't directly talking about making as many alternative purchase channels as possible. )
High Throughput? The memory subsystem on the Ultra is pretty high. Double Ultra would be probably be twice as high. Decoding double digit number of 8K RAW video streams? That is high throughput.
What is missing is PCI-e v4 (or v5) general I/O in 'bulk'. Hanging that off of an augment to UltraFusion wouldn't be took hard. ( put two x16 PCI-e v4 controllers and would have more than decent bandwidth/throughput given the GPU is covered internally and not a necessarily a huge consumer. )
The other thing that has changed over last 5 years is that there is a bigger pool of software that can leverage "Compute GPUs". For "embarrassingly parallel" workloads chopping workloads up into more chunks and spreading them out over multiple "compute accelerators" works well. Fabrication and packaging constraints limit just how big can make a single , large GPU... and two-three largish ones can spread more load than a singles large one can. Apple may not want to let "display GPU" drivers back into the mix, but "compute accelerator" drivers will be a gap for highest end workloads.
If the SoC "card" has the RAM , SSD drive , probably the TB sockets (as the primary video out ports ) .... what exactly is substantively left on the rest of the board?
Replace cost for that or replacement cost for a motherboard is going to be significantly different how?
[ compared to Mac Pro 2019 board can dump the DIMMs slots, relatively complex DisplayPort routing, dual feed PCI-e switch. most of that got subsumed into the SoC package. ]
Neither macOS nor their Apple GPU drivers support that "Multiple SoC" notion at all.
Apple has at every opportunity explicitly cheerleaded the notion that "Unified Memory" is 'insanely great' and a key lynchpin to their approach. Pretty unlikely they are going to throw that out the window at this point for a small single digit percentage, practically "hobby" product.
i highly doubt it will be PCIE slots, apple will probably engineer yet another proprietary connector, which sucks but is expected. maybe they will make the connector licensable or something so that third parties can make cards, but that's pretty unlikely. these slots will probably be the only form of "upgrade", which is a pretty loose term in the age of AS.
going on a slight tangent, i don't consider the 2013 trashcan to be a "real mac pro", it's basically the mac studio before the mac studio - a non-expandable compact workstation, which is a totally different product class than a box with slots.
when i think of "mac pro", i think of the old 2010 style and 2019 style - a box with slots, fully upgradeable and expandable using standard components and connectors. hopefully the new AS mac pro at least tries to keep in line with that philosophy.
honestly i just wish the 2019 mac pro was bit cheaper, since it's pretty much the closest thing to a "standard pc" apple has ever made in recent history, and just like the 2010 people will still be using it 10 years later. no doubt in ~5 years it will become much cheaper secondhand as all the real pros either switch to windows/linux or their pro apps work on AS, and especially once data centers start liquidating their xeons for a few hundred a piece.
hopefully the rumor of an intel mac pro refresh is true, and they actually do it justice with the latest xeon lineup, pcie 5.0, and all the other modern features that were lacking from the 2019... and this time make it space grey
Mac Pro needs to nothing like the 2013 mac pro. Done.
If they solder the memory it better be HBM3 memory, then I won't mind and it should have slots. Apple sgould also make dGPUs.
Apple doesn't really do standard generic LPDDR4/5. What Apple does is much closer to a semi-custom 'poor man's ' HBM2-3 memory than generic LPDDR. It is much wider and to a non standard RAM packages. That brings it into similarity with HBM technics only the bus and RAM packages are more affordable. But soldering them done is pragmatically also required.
Apple is getting very competitive aggregate bandwidth out of their Memory subsystem. It isn't like generic DDR4/DDR5 is going to be faster. Could burn more power to get to larger Max capacity thresholds but not loosing anything throughput.
At this point it isn't like other folks are going down a similar path.
https://www.servethehome.com/nvidia-grace-2xhopper-supercomputer-building-block-at-gtc-2022/
Soldered down LPDDR5X there also and not using HBM3 ( like the "Hooper" GPU in other package combos).
Is Apple going to use the same kind of outer area and mount points for their package? Probably not. (the variety of systems will be constructing at the high end will be probably be just one. )
I still think Apple will use LPDDR5X SDRAM for the ASi Mac Pro, and it looks like it could also be ECC...?
Seems like I misunderstood what MPX meant, I didn't realize it was specifically the 2 connector PCIE cards. Regardless, in my head I was thinking of Apple's PCIE cards in their custom enclosure with the big heat sink and mounting screws designed specifically to bolt into the MP chassis. My guess was if the new MP has slots, it will be with similarly designed but smaller cards using a single proprietary connector. I'm not too familiar with the 2019 cheesegrater MP in terms of third party cards, and wasn't aware that there were effectively no third party offerings. Based on what we've seen in the Mac Studio, I'd wager if the new MP has any slots/upgradeability it will be some proprietary Apple solution, which is why I suspect it won't have any standard PCIE connectors. I also doubt these slots will support discrete/additional GPUs since Apple seems dead set on the integrated die approach of combining CPU/GPU/RAM into one SOC, and almost certainly won't support slotted discrete GPUs. I don't know enough about integrated SOCs to say if it's technically possible or not, I'm just guessing they won't do it (unless they can charge absurd $$$ for it, assuming it is possible).Slots 1 and 3 in the MP 2019 have two connectors. One is regular standard x16 PCI-e v3. The other is the MPX connect that does the augmented stuff the MPX modules need. There were no 3rd party cards except for a limited (likely misadventure) storage offering in the form of the Promise R4i RAID MPX module. So if Apple went even more proprietary there would more likely be less than one 3rd party card.
I worded this poorly. I meant that in ~5 years, most of the "real pros" using the 2019 MP for real work will probably have moved on to a more capable/modern system - whether the replacement is AS or Windows/Linux remains to be seen. When these work/business machines are liquidated, they will be bought up a variety of people, ranging from "prosumers" to "real pros with less budget" that still want to use them ("prosumers" being the type of people who aren't using it for a job or "real work", but still want "pro" or unique/different hardware, even if it's a little dated). This happened with the previous MPs. Even the 2010 MP is bought/used by people, judging by the amount of MP 1,1-5,1 posts on this forum. I obviously can't quote numbers, but I have seen pictures/videos on YouTube and other places of 2013 trashcan MPs in use today ranging from small music studios, to small photo/video studios, to people like me and others who just like the design and don't mind using older hardware since we aren't using it for business/work purposes.'real pros' and folks whose business plans are wholly contingent on buying up used e-waste from datacenters to get 'real' work done is probably not a large intersection.
...Seems like I misunderstood what MPX meant, I didn't realize it was specifically the 2 connector PCIE cards. Regardless, in my head I was thinking of Apple's PCIE cards in their custom enclosure with the big heat sink and mounting screws designed specifically to bolt into the MP chassis. My guess was if the new MP has slots, it will be with similarly designed but smaller cards using a single proprietary connector. I'm not too familiar with the 2019 cheesegrater MP in terms of third party cards, and wasn't aware that there were effectively no third party offerings.
Sorry for any confusion, a lot of this isn't in my area of familiarity.