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2018 Mac Mini PCIe Lane\TB3 Discussion Lounge

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killawat

macrumors 68000
Original poster
Sep 11, 2014
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Ok so the new Mac mini is here. I, a staunch MBP enthusiast, am planning to buy, but lets take some wagers on the situation regarding the max perf we can get out of TB3 port. Anyone thinking we can get full bandwidth on each? Probably not as that would require a separate thunderbolt controller for each. I say this without looking at the CPU configuration, which I'll do later.

What about that 10 Gbit port? Wonder if they will drop one of the TB3 controllers down to 2 lanes to accommodate Aquantia controller.

Code: 
Support for the following combination of maximum concurrent display setups:
Up to three displays:
Two displays with 4096-by-2304 resolution at 60Hz connected via Thunderbolt 3 plus one display with 4096-by-2160 resolution at 60Hz connected via HDMI 2.0
or
Up to two displays:
One display with 5120-by-2880 resolution at 60Hz connected via Thunderbolt 3 plus one display with 4096-by-2160 resolution at 60Hz connected via HDMI 2.0

The video capabilities of the Mac mini don't reveal much. The maximum 2x 4k or 1x 5k display is probably limited by the iGPU.

Unlike everyone else I'm not hugely concerned by the lack of dGPU. Yeah, it would have been nice at this price point, but that means we get more bandwidth allocated elsewhere, hopefully to TB3 controllers.

Edit: Someone over at appleinsider said that he believes all four TB3 ports are on one controller. I don't buy that for a nanosecond. AppleInsider's Mac mini FAQ

Four Thunderbolt 3 ports! Does that mean I can have four 5K displays?

Nope. It appears that the four ports are on one controller. Practically, this means that a user can have two displays with 4096 x 2304 resolution at 60Hz connected via Thunderbolt 3, plus one display with 4096 x 2160 resolution at 60Hz connected via HDMI 2.0. Alternatively, the user can have one display with 5120 x 2880 resolution at 60Hz connected via Thunderbolt 3 plus one display with 409 x 2160 resolution at 60Hz connected with the HDMI 2.0 port.
Click to expand...

This configuration would obviously neuter the functionality of every other port if a hungry device like an eGPU were attached.
 
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Yeah I'm a bit curious myself.

The CPU's DMI + PCIe lanes add up to about 160Gb/s maximum.

The three display configuration implies two DP links over TB and one via the HDMI connector. The two DP links are independent from PCIe/DMI, so that's theoretically another 34ish Gb/s.

However, the SSD is probably 4 lanes of PCIe (32Gb/s) and then you have another 20ish (likely also 4x PCIe) Gb/s for the 10GbE.

So the answer seems to be a firm no, it's not going to be possible to get 160Gb/s out of the 2018 Mac Mini's TB ports, especially with 10GbE.

If I were to wager a wild guess, I would say maybe two Thunderbolt controllers will be present? Apple's probably expecting a use case involving a mixture of Display Port, USB-C, USB-A and Thunderbolt, not maxed out quadruple TB3.
 
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Can any lucky souls post an output of their MM 2018 Thunderbolt Device Tree from System Information? These commands work too:

Show Thunderbolt Bus
Code: 
system_profiler SPThunderboltDataType | grep -E 'Thunderbolt Bus'

Show Thunderbolt Bus and Port Speeds
Code: 
system_profiler SPThunderboltDataType | grep -E 'Speed|Thunderbolt Bus'
 
killawat said:
Can any lucky souls post an output of their MM 2018 Thunderbolt Device Tree from System Information? These commands work too:

Show Thunderbolt Bus
Code: 
system_profiler SPThunderboltDataType | grep -E 'Thunderbolt Bus'

Show Thunderbolt Bus and Port Speeds
Code: 
system_profiler SPThunderboltDataType | grep -E 'Speed|Thunderbolt Bus'
Click to expand...

It's as I thought, two controllers (note I have a TB2 audio interface plugged into one of the ports):

Code: 
Thunderbolt Bus'
    Thunderbolt Bus 1:
          Speed: Up to 40 Gb/s x1
          Speed: Up to 40 Gb/s x1
    Thunderbolt Bus 0:
          Speed: Up to 40 Gb/s x1
          Speed: Up to 20 Gb/s x1
              Speed: Up to 20 Gb/s x1
              Speed: Up to 20 Gb/s x1
 
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rmdeluca said:
It's as I thought, two controllers (note I have a TB2 audio interface plugged into one of the ports):
Click to expand...
Yep, perfect. No one port nonsense not that I even believed that for a second. Still wanted to have 3x 40 Gb/s controllers but 2x will do. Can only have two eGPUs now :)

Thanks
 
rmdeluca said:
It's as I thought, two controllers (note I have a TB2 audio interface plugged into one of the ports):

Code: 
Thunderbolt Bus'
    Thunderbolt Bus 1:
          Speed: Up to 40 Gb/s x1
          Speed: Up to 40 Gb/s x1
    Thunderbolt Bus 0:
          Speed: Up to 40 Gb/s x1
          Speed: Up to 20 Gb/s x1
              Speed: Up to 20 Gb/s x1
              Speed: Up to 20 Gb/s x1
Click to expand...
Why is one port limited to 20 Gbps?
 
enri1357 said:
2 bus, good or bad?

and, compare to MBP2018 15"?
Click to expand...

IMO, it's pretty awesome. For someone like me it means I can run a pro audio interface and eGPU and they'll each get their own independent PCIe lanes.

I think the 2018 MBP has two Thunderbolt controllers as well (it has four ports), but it doesn't have USB-A ports. Besides the physical lack of space for USB-A ports, I think the MBP also has to contend with the fact that 8 PCIe lanes are dedicated to the dGPU, unlike the Mini which has an iGPU, freeing those lanes up for other uses.
 
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I see. This is great, as no compromise and top of the class until we see the next Mac Pro (which I won't buy anyway)

Thanks for explaining
 
rmdeluca said:
IMO, it's pretty awesome. For someone like me it means I can run a pro audio interface and eGPU and they'll each get their own independent PCIe lanes.

I think the 2018 MBP has two Thunderbolt controllers as well (it has four ports), but it doesn't have USB-A ports. Besides the physical lack of space for USB-A ports, I think the MBP also has to contend with the fact that 8 PCIe lanes are dedicated to the dGPU, unlike the Mini which has an iGPU, freeing those lanes up for other uses.
Click to expand...
How come the MBPro can drive two 5K displays then? Is this due to a GPU limitation? And thus, would adding an eGPU to the MM enable two 5K displays? (one internal, one via eGPU).
 
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Spectrum said:
How come the MBPro ca drive two 5K displays then? Is this due to a GPU limitation? And thus, would adding an eGPU to the MM enable two 5K displays? (one internal, one via eGPU).
Click to expand...
Yep, the dGPU can power 2x 5k Displays but literally nothing else, the bandwidth to the Thunderbolt 3 ports will be maxed out!

But yes, you can also power 2x 5k Displays with an eGPU. Depending on the eGPU you get and your monitor type (i.e. one that accepts DisplayPort), you can get two eGPUs or one eGPU with a GPU that supports multiple 5k displays (as long as it's AMD). Sky's the limit.
 
killawat said:
Yep, the dGPU can power 2x 5k Displays but literally nothing else, the bandwidth to the Thunderbolt 3 ports will be maxed out!

But yes, you can also power 2x 5k Displays with an eGPU. Depending on the eGPU you get and your monitor type (i.e. one that accepts DisplayPort), you can get two eGPUs or one eGPU with a GPU that supports multiple 5k displays (as long as it's AMD). Sky's the limit.
Click to expand...
So with 2 eGPUs (each with the DP outputs) the 2018 MM could actually, in theory, drive 4x5K displays? Plus a 4K from the HDMI? What about from the other TB3 ports? Would they then be saturated?
 
Spectrum said:
So with 2 eGPUs (each with the DP outputs) the 2018 MM could actually, in theory, drive 4x5K displays? Plus a 4K from the HDMI? What about from the other TB3 ports? Would they then be saturated?
Click to expand...

Yep. Basically you can saturate a TB3 connection with a 5k display powered by the iGPU, or you can saturate it with an eGPU connection but that gives you as many display options as is supported by the GPU. The other two ports you might be able to plug in maybe like a USB 2.0 device but really, resource contention is a tricky subject for Thunderbolt. More than likely it would manifest itself with your 5k screen cutting in and out if you happened to plug something else in. For the most part, we know that eGPU will expect and consume all the bandwidth on a given TB3 port, so the other two will need to stay empty, and then add on an additional device or two at a time before things get cut off. I would not expect to use those extra ports at all with eGPU running alongside.
 
killawat said:
For the most part, we know that eGPU will expect and consume all the bandwidth on a given TB3 port, so the other two will need to stay empty, and then add on an additional device or two at a time before things get cut off.
Click to expand...
Doesn't compute. I think you are confusing allocating PCIe lanes vs. using PCIe lanes. Why would the eGPU consume all of the TB3 bandwidth? That would put the load back on the CPU. The eGPU communicates with the CPU and memory but only as needed. TB is designed to share PCIe lanes but an eGPU may restrict/negotiate dedicated access.
 
rmdeluca said:
No, the PCIe lanes dedicated to ethernet are different from the ones dedicated to the TB3 controllers. Hence why I argue vociferously for getting the 10GbE option IF you plan on using your Mini with fast NAS and eGPU.
Click to expand...

Right, through the PCH. (I ordered the 10GbE option)
 
Hi, 10GbE owners, do you experience network issues when you install Bootcamp Windows 10 on your machine? just right now, I installed a copy of Windows 10 (1803 then upgrade to 1809) and it is behaving strange. The ethernet connection will disable itself within 2 mins of boot up, and the machine will not restart after that. A restart will lead to a 3 mins black screen and eventually shutdown itself. When I boot back to macOS, it give me Bridge OS error.

Do you see similar issues with Bootcamp? (Apple support decline help saying that my mini on Mojave is working fine and ask me to ask Microsoft....)
 
rmdeluca said:
No, the PCIe lanes dedicated to ethernet are different from the ones dedicated to the TB3 controllers. Hence why I argue vociferously for getting the 10GbE option IF you plan on using your Mini with fast NAS and eGPU.
Click to expand...


I would argue an external brick allowing both a removable nvme m.2 and a sata drive inside would be better. But since it was not done you are stuck with getting a 10gbe and of course a 10gb switch.

Did you do this? If so what 10gbe nas and what 10gb switch did you get.
It seems the only way I would buy the 2018 is going 10gb switch and nas along with egpu.

Get the i7 get a 256gb internal get an egpu the nas and the switch.

Fill the nas with some sata ssds.
 
enri1357 said:
Hi, 10GbE owners, do you experience network issues when you install Bootcamp Windows 10 on your machine? just right now, I installed a copy of Windows 10 (1803 then upgrade to 1809) and it is behaving strange. The ethernet connection will disable itself within 2 mins of boot up, and the machine will not restart after that. A restart will lead to a 3 mins black screen and eventually shutdown itself. When I boot back to macOS, it give me Bridge OS error.

Do you see similar issues with Bootcamp? (Apple support decline help saying that my mini on Mojave is working fine and ask me to ask Microsoft....)
Click to expand...

The very first time I booted into Windows (1809 upgraded from 1803) and played Fallout 76, the 10GbE lost connection and wouldn't come back until I rebooted. However, in the hundreds of hours I've been playing games in Boot Camp since then, I've not seen a recurrence of this problem even once.

I don't subscribe to the school of "it fixed itself" but I'd say in this case (going on several weeks now) a Windows update probably resolved the problem.
 
rmdeluca said:
The very first time I booted into Windows (1809 upgraded from 1803) and played Fallout 76, the 10GbE lost connection and wouldn't come back until I rebooted. However, in the hundreds of hours I've been playing games in Boot Camp since then, I've not seen a recurrence of this problem even once.

I don't subscribe to the school of "it fixed itself" but I'd say in this case (going on several weeks now) a Windows update probably resolved the problem.
Click to expand...

Thanks for your reply.

It turns out I need to manually update the driver from the AQN website to get it works without further problems. Previously the default is on July drivers version end with 8, and now with latest end with 12 it works :D
 
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