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Apple Silicon Mac Pro uses PCIe switches to support all slots

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Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#41

Post by ohgodplsno »

Zetobal wrote: post #31
goosedragons wrote: post #5

Earlier quoted context omitted.

You already can't add GPUs but since there's only 16 real lanes and a GPU can use 16 lanes it could cause issues. I would think this would lead to bottlenecks for instance if you were trying to write to two different 16x PCIe SSD RAID cards simultaneously.

No, GPU is even close to saturate 16 lanes.

Saturating 16 lanes is very doable, although for a very short amount of time. You'll never see it last more than half a second at absolute worst on normal usage, maybe more if you're trying to upload on a 192GB GPU or something. But since most uses evict data out of GPU RAM before writing instead of blindly overwriting, it's not a problem you could ever reasonably have.

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#42

Post by ceejayoz »

numpad0 wrote: post #33
c00lio wrote: post #3

Apple Silicon is low-power low-end laptop hardware. Of course their I/O capabilities are limited, because their users do not need lots of I/O. If you are looking for stuff with lots of I/O capabilities you have to buy proper server hardware.

I wouldn't call M2 Ultra a low-end, but it certainly qualifies as regular desktop CPU, rather than a server or workstation CPU. Xeon, EPYC, Threadripper typically has 128 lanes. 16+8 is Core/Ryzen configuration with x8 for chipset and x16 for GPU. It is really starting to look like either COVID and new Campus architecture had seriously crippled engineering capabilities of Apple, or if not all the capabilities are red…

> They could have made Pro a cluster supercomputer on a backplane just as a flexing and a nod to NeXT, but didn't.

Apple is crippled because they didn’t prioritize a niche use for the sole purpose of “flexing”?

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#43

Post by matwood »

varispeed wrote: post #9
wkat4242 wrote: post #6

Earlier quoted context omitted.

Of course Apple positions this as a proper workstation.

I remember being downvoted for saying this is essentially a phone CPU and motherboard, just without consideration for constraints imposed by the phone's footprint. It means it can be designed with higher TDP in mind etc. and yet, Apple charges for it as if it was a real workstation equipment rather than a phone in a massive enclosure.

> and yet, Apple charges for it as if it was a real workstation equipment rather than a phone in a massive enclosure.

Ignoring the no true scotsman argument, I'm not sure this is even an insult. Apple improved their phone CPUs to the point where they compete very well in the desktop space and in some workstation (for any meaning of this term) environments. It's what Intel did to traditional workstation vendors long ago, and is classic Innovators Dilemma. Typically that happens from a small startup and not some industry leading company though. Shame on Intel and AMD for not seeing this coming, since it had been telegraphed for years.

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#44

Post by nottorp »

teruakohatu wrote: post #2

What is the consequence of this? Does it limit the theoretical ability to add GPUs?

Well mac os doesnt support non Apple gpus any more. And if you want to run Linux with a bunch of compute GPUs Im sure there are more appropriate solutions than Apple hardware.

Not sure how this affects the use case of multiple video capture cards writing to fast internal storage that I see mentioned here and there. Anyone close to that industry around to comment?

Edit: i think I’ve seen mentioned that the PSU in this thing is “only” 1400W. That only covers one modern nvidia gpu right? :)

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#45

Post by ohgodplsno »

trollied wrote: post #40
meindnoch wrote: post #29

Earlier quoted context omitted.

What is exactly the use case for hot-swapping CPUs?

Swapping a failed device for a working one, without powering down the machine.

Curious to see how you imagine swapping all the registers and caches of a currently broken CPU (so, unable to do anything including sending those registers somewhere).

Because if you don't, sure, you didn't technically power down your machine, you just fucked up your entire stack, stack pointer goes to the wrong place, checks based on hardware are now wrong... In effect, you powered down the machine because your OS will just stop working, your running processes are fucked, etc.

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#46

Post by matwood »

nordsieck wrote: post #30
gumby wrote: post #26

Earlier quoted context omitted.

Maybe the “pro max” version of next September’s iphones. The iPad Pro versions have had TB3 for a while (though they ship with M2 CPUs, not the A series). Not really sure how many ppl would use this but if apple switches to Type C connectors they’re more likely to strut it at the high end than just just mention it in passing. The use case isn’t that clear to me. Perhaps a photographer, for a phone with a couple of TB…

> The use case isn’t that clear to me. Perhaps a photographer, for a phone with a couple of TB of SSD. IMO, eventually, phones will replace low end desktop/laptop computers. Someone (probably Apple, since their CPUs are head and shoulders above the competition) will have to do the work of designing a mode switching UI, but once that's done, they'll really be able to cut into desktop volume. I'm sure the early devices…

There's a bit of this version of the future in the iPad. Bluetooth keyboard and mouse, and plug into a 5k monitor. It shouldn't be hard to open it up on the phone (along with the basic window management).

It's also not really new, and has been tried many times in the past. I do think we finally have all the requisite technology in place though. BT peripherals mostly work, phones CPUs are powerful, phone apps are plentiful, etc...

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#47

Post by wongarsu »

dijit wrote: post #21
sprash wrote: post #20

If you have switched PCIe anyways I would have loved a Mac Pro with a "passive" switched PCIe backplane where you can hotplug PCIe devices in including M2 CPU PCIe cards. Also polish the OS accordingly that you can upgrade/switch your CPU in live operations without shutting down the OS or may be even run Apple silicon CPUs and x86 CPUs alongside.

I think we collectively decided that we didn't want hot-swap CPUs and instead wanted inexpensive compute (so we could have a lot more of it) when we let SPARC die.

I believe IBM Z Systems still have hot-swappable CPUs. Of course that one is also niche for the same reason: we prefer lots of cheap commodity servers instead of few super reliable rack-sized computers

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#48

Post by numpad0 »

danpalmer wrote: post #13
c00lio wrote: post #3

Apple Silicon is low-power low-end laptop hardware. Of course their I/O capabilities are limited, because their users do not need lots of I/O. If you are looking for stuff with lots of I/O capabilities you have to buy proper server hardware.

Not defending the Mac Pro's architecture here, I think there are issues, but calling Apple Silicon "low-end laptop hardware" is just false. The Max/Ultra chips easily outperform most server-grade CPUs, and are similar to top end Intel i9 chips. Then if you also take into account performance per watt, they're in a whole different league.

> top end Intel i9

Intel top end is Xeon. i9 is gamer CPU, more or less.

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#49

Post by numpad0 »

ohgodplsno wrote: post #45
trollied wrote: post #40

Earlier quoted context omitted.

Swapping a failed device for a working one, without powering down the machine.

Curious to see how you imagine swapping all the registers and caches of a currently broken CPU (so, unable to do anything including sending those registers somewhere). Because if you don't, sure, you didn't technically power down your machine, you just fucked up your entire stack, stack pointer goes to the wrong place, checks based on hardware are now wrong... In effect, you powered down the machine because your OS w…

Mainframes has been doing hot-swapping everything for decades. OS and motherboard is just supposed to tolerate multiple CPU crashes. Technical feasibility of that is a long-solved problem, only economically it's dubious.

Re: Apple Silicon Mac Pro uses PCIe switches to support all slots

#50

Post by nordsieck »

matwood wrote: post #46
nordsieck wrote: post #30

Earlier quoted context omitted.

> The use case isn’t that clear to me. Perhaps a photographer, for a phone with a couple of TB of SSD. IMO, eventually, phones will replace low end desktop/laptop computers. Someone (probably Apple, since their CPUs are head and shoulders above the competition) will have to do the work of designing a mode switching UI, but once that's done, they'll really be able to cut into desktop volume. I'm sure the early devices…

There's a bit of this version of the future in the iPad. Bluetooth keyboard and mouse, and plug into a 5k monitor. It shouldn't be hard to open it up on the phone (along with the basic window management). It's also not really new, and has been tried many times in the past. I do think we finally have all the requisite technology in place though. BT peripherals mostly work, phones CPUs are powerful, phone apps are plen…

> It's also not really new, and has been tried many times in the past.

The trouble with the future is that, even if you know that it's inevitable, you may be too early for that to matter.

There are a huge number of dot com busts that later became successes (different company, though) because we have the needed technology today.

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