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cconnection
(@cconnection)
New Member
Joined: 2 years ago
 

Hi everyone,

I am also interested how the mac mini performs with an egpu. I‘m looking forward to buy a mac mini 6-core i7 3,2 GHZ (4,2GHZ) with an razer core x, sapphire nitro+ vega56 8G HMB2 and upgrade it with 32gb myself. I‘m not quiet sure about internal storage, whether I upgrade the internal storage or stick wirh 128gb and attach an external ssd.

I‘m also curious about the thunderbolt controller and throttling. We‘ll hopefully know more next week. I am going to wait to pull the trigger until we know more about the internals.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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DanHC
(@danhc)
Eminent Member
Joined: 2 years ago
 
Posted by: itsage

@danhc Every single Thunderbolt Mac I tested has at most 2 ports per Thunderbolt controller. The controllers themselves can only host up to two ports. It's impossible for Apple to pair four functional Thunderbolt 3 ports to one controller. The Mac mini will likely have two Titan Ridge controllers attach directly to the CPU. The 16 PCIe lanes will probably be split three way: x8 to 10GbE, one x4 each to the TB3 controllers. Flash storage goes through the T2 chip and wireless card goes through the PCH.

The one 5K monitor output limitation as you found is due to the weak Intel iGPU. The system combines two DisplayPort streams to provide 5K @ 60 Hz over Thunderbolt 3. It would be great if we have access to the system block diagram. Here are the diagrams of the 2013 Mac Pro and 2017 iMac Pro for example.

@rohela1122 Please share the article you read that stated the Mac mini has only one Thunderbolt 3 controller.

You are right. Looking at ark of Intel

https://ark.intel.com/products/series/79641/Thunderbolt-Products

All TB controllers are either Single or Dual Port configuration.

Now I am wondering how Apple could make it into four ports, if what @rohela1122 said is true, my understanding is that TB can be daisy chained but cannot be spitted.

Update: I don't know where @rohela1122 got his information, but this article from Appleinsider says there is only one controller

https://appleinsider.com/articles/18/10/30/frequently-asked-questions-about-the-2018-mac-mini-ram-storage-and-more

"It appears that the four ports are on one controller." It might be referring to other controllers other than TB, or just plain wrong.

2013 15" MacBook Pro (GT750M) [4th,4C,H] + RX Vega FE @ 16Gbps-TB2>TB3 (Sonnet Breakaway 650) + Win10 [build link]  

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expensivefruit
(@expensivefruit)
Eminent Member
Joined: 2 years ago
 

Is there a particular reason why the lack of multiple thunderbolt controllers is an issue, other than the obvious fact that you cannot connect more than one 5K screen to the mini? Or is it because you cannot connect both a 5K screen and an eGPU because of bandwidth limitations? I'm trying to figure out what the best possible case scenario is (assuming one thunderbolt controller) in terms of what and how many screens you can use along with the eGPU and what the routing will look like. I should stress again that I'm a novice on this forum and still trying to get to grips with everything.

Edit: My apologies. Having read other replies above I now realise that having more than one controller allows to free up resources to solve error 12. Let's hope error 12 doesn't happen, although I guess we will have to wait for someone to take one for the team and try it! 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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itsage
(@itsage)
Illustrious Member Admin
Joined: 4 years ago
 

@danhc That AppleInsider article is inaccurate. There's no one Thunderbolt 3 controller that can host more than two ports. Look at all existing Macs with 4+ Thunderbolt ports. They have multiple Thunderbolt controllers. Each controller hosts two ports.

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2020 13" MacBook Pro [10th,4C,G] + RX 5700 @ 32Gbps-TB3 (Prototype eGPU Enclosure) + macOS 10.15.4 & Win10 1903 [build link]  


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DanHC
(@danhc)
Eminent Member
Joined: 2 years ago
 
Posted by: itsage

@danhc That AppleInsider article is inaccurate. There's no one Thunderbolt 3 controller that can host more than two ports. Look at all existing Macs with 4+ Thunderbolt ports. They have multiple Thunderbolt controllers. Each controller hosts two ports.

Thanks for the info, I think AppleInsider is wrong too. After checking ARK of intel myself, I don't think that's possible unless Apple once again pull off some kind of Frankenstein machine.

2013 15" MacBook Pro (GT750M) [4th,4C,H] + RX Vega FE @ 16Gbps-TB2>TB3 (Sonnet Breakaway 650) + Win10 [build link]  

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expensivefruit
(@expensivefruit)
Eminent Member
Joined: 2 years ago
 

@danHC having read through the comments in that article, one user did question the argument as to whether really is only one controller. It may have even been someone from this forum. This was the response from one of the admins in the comments: 

"We've been told there's only one controller. Alpine Ridge allows for it, but we will ultimately have to wait for the tear down. Given that the MacBook Air CPU wasn't in Intel's ARC until about 2PM, there is a distinct possibility that it is a custom SKU or the first rollout".

Thoughts? 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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DanHC
(@danhc)
Eminent Member
Joined: 2 years ago
 
Posted by: expensivefruit

@danHC having read through the comments in that article, one user did question the argument as to whether really is only one controller. It may have even been someone from this forum. This was the response from one of the admins in the comments: 

"We've been told there's only one controller. Alpine Ridge allows for it, but we will ultimately have to wait for the tear down. Given that the MacBook Air CPU wasn't in Intel's ARC until about 2PM, there is a distinct possibility that it is a custom SKU or the first rollout".

Thoughts? 

"We've been told there's only one controller."
So it is just hearsay, no point on commenting on the technicality part. 

"Alpine Ridge allows for it"
My question: How?  Alpine Ridge is a older TB3 controller, all existing documentation state that the maximum ports an Alpine Ridge controller (as well as new Titan Ridge controller) can drive is two. So reading the statement solely base on existing publicly available information, it is an incorrect statement.

"but we will ultimately have to wait for the tear down" 
4 Days to go

"Given that the MacBook Air CPU wasn't in Intel's ARC until about 2PM, there is a distinct possibility that it is a custom SKU or the first rollout."
For the 1st Part, yes it not the first time apple use part from Intel exclusively release for for Apple, with no mention of it before Apple's release. Like the Intel® Intel Core i5-8210Y with UHD Graphics 617 the new Macbook Air uses, no information of it whatsoever before Apple Announcement.

Take a look at the 10 core model of iMac Pro, it comes with a Xeon W-2155B, which is identical to Xeon W-2155 CPU people can get in retail in every single way, except the base clock is 300Hz lower (3Ghz vs 3.3Ghz), my guess is that Apple get those CPUs with lower bin quality that would otherwise discarded by Intel at a cheaper price. It isn't some special version of CPU that is required to keep the iMac Pro working either. A Youtuber (Snazzy Lab) replaced the iMac Pro CPU with standard Xeon W-2155 CPU and it works, even faster.

It is not uncommon for Intel, AMD, Nvidia to re-brand their product even if it is based on the same manufacturing chip, but making a older generation product capable to do things that even the new Titan Ridge controller cannot do, with a new design functionality that is unheard of, I am skeptical about that possibility.

If the new Mac Mini comes out in one controller with four ports, I think it is rather likely that it is Apple who implement some sort of M****r-f***ing solution with an existing chip to make it happen over the possibility that Intel made a new chip. Like the original iMac 5k, the GPU inside that iMac is Tonga without HDMI 2.0 or DP 1.3. Oh okay, let's make a custom TCON with a a non-standard 60-pin Embedded DisplayPort to make it work. 

Posted by: expensivefruit

Is there a particular reason why the lack of multiple thunderbolt controllers is an issue, other than the obvious fact that you cannot connect more than one 5K screen to the mini?

If there is only one controller, bandwidth limitation will be shared by all TB ports, using 5K monitor for instance, will take up almost all its bandwidth, leaving not much left for the eGPU, i wouldn't say it can't, but so severe limited that it will close to unusable.  So with one controller, using a 5K display or a eGPU will just kill the bandwidth for the three remaining ports. (Display link is prioritized in TB3, so if eGPU and 5K monitor are connected through the same controller, it is the eGPU suffers).   (Put simply, bandwidth of eGPU + bandwidth of operating 5K monitor > bandwidth of one TB controller).

For my Macbook Pro Late 2013, there are two Thunderbolt 2 ports (under one controller). When I connect a 4K display with it with one of the ports and eGPU on another, the monitor connects to the eGPU become super laggy like having 5Hz refresh rate. It takes roughly 17.2Gbps of bandwidth to drive a 4K @ 60 fps, leaving 2.8 Gbps for the eGPU for the second 4K monitor. Thunderbolt 2 has 20Gbps of bandwidth.

I will not get the new Mac Mini if it has only one TB controller. It means once I connect two 4K monitor / one 5K monitor or a eGPU with one of the ports, the remaining ports become useless ports and the expand-ability becomes close to zero. 

Sorry it's a long reply with some irrelevant information, that's all I could guess right now.

2013 15" MacBook Pro (GT750M) [4th,4C,H] + RX Vega FE @ 16Gbps-TB2>TB3 (Sonnet Breakaway 650) + Win10 [build link]  

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expensivefruit
(@expensivefruit)
Eminent Member
Joined: 2 years ago
 

@DanHc thank you taking the time to write all that, I wholeheartedly hope you are right with your analysis! 

I decided to do a bit more research and see if I could read anything between the lines in Apple's marketing campaign. I realise this isn't exactly scientific evidence or analysis, but I thought this particular paragraph from the main page about the mac mini on the Apple website would be pertinent to share: "Connect up to two 4K displays — and even a third with HDMI 2.0 — or one 5K display. Or pair Mac mini with an eGPU for desktop-class graphics performance". The telling word, which I have bolded, is OR, which would imply that you can't connect BOTH an eGPU and use a 5K display (or two 4K displays). 

The thing is, using a 5K display is not a dealbreaker for me. Of course, it would be nice, but I'm quite happy connecting one 4K display over TB3 and another over HDMI. I would also presume there is an option to connect another one over USB 3, or am I wrong here? My bigger concern is this idea that a second controller is critical in order to free up resources to resolve a potential error 12, but unfortunately I'm not well versed in this issue. 

I suppose the more important question to ask, assuming there is only one controller, is this: why on earth would Apple cannibalise the mac mini in this way? Why not just have 2 controllers? Is this a ploy to protect their upcoming Mac Pro line? Given how much more powerful one would expect those machines to be it would seem to be completely illogical to do something like that. 

 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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joevt
(@joevt)
Noble Member
Joined: 3 years ago
 

Maybe it has two controllers, but only one has DisplayPorts connected to it (to support 5K with Dual Link-SST)? The third output of the iGPU is the HDMI port. That would mean you couldn't connect displays to two of the ports. That isn't mentioned anywhere, so maybe there's some kind of MUX that lets both controllers use the same two DisplayPorts...

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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joevt
(@joevt)
Noble Member
Joined: 3 years ago
 

https://egpu.io/forums/which-gear-should-i-buy/2018-mac-mini-for-egpu/paged/2/ Test NVMe one per port / raid.

Posted by: DanHC

Just to be clear, what I am commenting is based on the feasibility of the above-mentioned setup of 

"Connection : eGPU - (TB3) - MacMini - (TB3) - 5K"

The reason I make a distinction between using one and two Thunderbolt controllers is that based on my limited understanding and research (which could be wrong), bandwidth is limited by the controller as a whole and not by individual ports, if there are two TB ports controlled by one controller, they share the same bandwidth limitation. (i.e. 40Gbps using one port under one TB controller, but 20Gbps (if equally shared) when connecting two equal device under 2 ports under the same TB controller)

So in the "Connection : eGPU - (TB3) - MacMini - (TB3) - 5K" scenario, if both (TB3) are connected in different ports under the same controller, they will have to share the bandwidth limitation of the same controller...

that is to say
Operation "eGPU - (TB3) - MacMini" 
Operation "MacMini - (TB3) - 5K" 
share by the same bandwidth of a single TB controller.

Please see (Is Intel's Thunderbolt 3 dual port controller's total data bandwidth 32gbps or 22gbps??)
https://communities.intel.com/thread/127679

"Either way, the maximum bandwidth for that single controller, which is around 2750 MB/s, will be shared among the two devices."
"Yes, the two ports share the same bandwidth. The 2750 MB/s is the actual transfer rate you can expect.For example, if you run a benchmark on a NVMe SSD that can go fast enough, it will max out around 2750 MB/s. If you test two at the same time, I would expect around 1375 MB/s per drive.""

I don't believe this is true. A single port is limited to 22 Gbps (PCIe bandwidth) or 2750 MB/s but I was able to get up to 2815 MB/s by raiding two NVMe devices together, one per Thunderbolt port of a GC-TITAN RIDGE in a GA-Z170X-Gaming 7 motherboard's PCH slot. I don't know if there's throttling that could be disabled to allow > 3000 MB/s or if this is the physical limit of the chip. Individually, the NVMe drives can go up to 2645 MB/s so 2815 MB/s isn't all that great. And I don't know how adding DisplayPort signals would affect this. I'll retest this with the Mac mini when it arrives.

Posted by: DanHC

That is why the Macbook Pro 13 can only connect to one ultrafine 5K even though it has two TB ports (under one controller), while the Macbook Pro 15 can connect to two ultrafine 5K, but need to connect to one of the ports at the left and one of the ports at the right (under two controller).
https://support.apple.com/en-us/HT207448

The UltraFine 5K requires two DisplayPorts. Each controller can have two DisplayPorts. So you can have one UltraFine 5K per controller.

Posted by: DanHC

The reason why the USB ports behind the Ultrafine 5K run at USB 2.0 speeds are because driving the 5K monitor alone have chewed up almost the entire bandwidth of TB3.
(As you have mentioned in your other post "4096 * 2180 pixels/frame * 30 bits/pixel * 60 frames/second = 15.9 Gbps for DisplayPort over Thunderbolt" and that 5K is almost twice as 4K, it really is close to nothing left driving a 5K monitor)

The USB ports of the UltraFine 5K are USB 3.0 (5 Gbps). 5K is 26.54 Gbps. Of DisplayPort. The 22 Gbps limit is only for PCIe. So out of 40 Gbps, 13.5 remains for PCIe. Problems may arise if using a eGPU with a display not connected to the eGPU:

Posted by: DanHC

Having said all the above, TB3 is bi-directional, so 40Gbps EACH WAY, and that getting the 5k feed from "eGPU - (TB3) - MacMini" is download and "MacMini - (TB3) - 5K"  is upload, I wouldn't say it could not work, but definitely not as ideal, bandwidth wise, compare to using two separate TB controller for two separate task.

Posted by: DanHC

https://egpu.io/forums/pc-setup/how-much-bandwidth-ovehead-does-optimusx-connect-accelerated-internal-lcd-mode-add/

Having said all the above, using the above chart, I doubt it is even feasible to send back 5k video back from the eGPU to the Mac-mini when 22Gbps (as data bandwidth for egpu), before passing it through the 5k Monitor.

Anything is feasible if you don't need it to be 60Hz. I mean that it will work but maybe not ideally as you've said.

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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