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Mid 2019 Mac Pro PCIe Slots and Thunderb...
 

Mid 2019 Mac Pro PCIe Slots and Thunderbolt 3 Add-in Card  

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theitsage
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Jun 3, 2019 11:51 pm  

With the introduction of the mid 2019 Mac Pro, Apple has brought internal PCIe slots back in a tower form factor. The excitement ends here for me. They priced me out completely. What I found most intriguing is the Thunderbolt 3 add-in card. This means when Thunderbolt 4 becomes available it's possible to upgrade (and hopefully used 2019 Mac Pro are within reach by then). It might be a possibility for the classic Mac Pro to use this AIC if it's available through third party.

Above is my guess of the PCI Express lane allocation to each slot. The CPU has 64 lanes so a PCIe switch is likely hosting slot 5 to 8. The MPX with its use of a modified/extended slot is pretty cool. From what I gathered Apple routed the two Thunderbolt 3 controllers on the MPX graphics card to a x8 PCIe connection. In a fully configured Mac Pro, there are 6x TB3 controllers and 12x TB3 ports.

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mac_editor
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Jun 4, 2019 1:19 am  

Apple: Here’s the new Mac Pro.
Me: Seems nice, monitor looks great.
Apple: Starts at 5999$.
Me: Well....
Apple: Here’s the new Apple Pro Display XDR.
Me: This is great.
Apple: Costs 4999$.
Me: Oh, well....
Apple: The stand is sold separately and costs 999$.
Me: ...

That stand should have a f***ing GPU in it, a good one at that.

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nu_ninja
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Jun 4, 2019 3:16 am  

I mean, the hardware specs look very impressive and I'd be lying if I said I didn't want one, even if I don't know what I would do with it.

But I get the feeling even Apple doesn't really know what they want to do with this. The base iMac Pro is $1000 cheaper and comes with a 5k display attached. Sure it's not as modular, but the CPU and RAM are still socketed and with an eGPU you could theoretically upgrade the graphics as well. I actually wouldn't be surprised if the price point is deliberately higher so it doesn't compete with the iMac Pro.

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+ macOS 10.14+Win10
+ Linux Mint 19.1


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Ningauble77
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Jun 4, 2019 5:49 am  

2019 Mac Pro was announced today with 580x base gpu but option for either single or dual Vega 20- based "Radeon Pro Vega II" cards, so hopefully Radeon VII drivers will improve as we approach the fall.  Also gives little hope to nvidia drivers going forward, considering the Mac Pro has PCIe slots, but semi-proprietary auxiliary connectors on the Graphics Cards to feed DisplayPort from the slots to the TB3 ports and may not even work with generic off-the-shelf GPUs.  Also had a bunch of pro-app companies announce Metal support for their software, some of whom I believe currently perform best with CUDA.

2018 13 Macbook Pro + Core v2 + Radeon VII Win10 1809/MacOS 10.14.5 Beta
ASUS X99 Deluxe+Core v2 + Radeon VII Win10 1809


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goalque
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Jun 4, 2019 5:49 am  
Posted by: Ningauble77

but semi-proprietary auxiliary connectors on the Graphics Cards to feed DisplayPort from the slots to the TB3 ports and may not even work with generic off-the-shelf GPUs.

No word about standard graphics cards. I was wondering if you can combine:

"Up to 300W auxiliary power via two 8-pin connectors"

and

"Three full-length PCI Express gen 3 slots
One x16 slot; two x8 slots
75W auxiliary power available"

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OliverB
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Jun 4, 2019 5:49 am  
Posted by: Ningauble77

2019 Mac Pro was announced today with 580x base gpu but option for either single or dual Vega 20- based "Radeon Pro Vega II" cards, so hopefully Radeon VII drivers will improve as we approach the fall.  Also gives little hope to nvidia drivers going forward, considering the Mac Pro has PCIe slots, but semi-proprietary auxiliary connectors on the Graphics Cards to feed DisplayPort from the slots to the TB3 ports and may not even work with generic off-the-shelf GPUs.  Also had a bunch of pro-app companies announce Metal support for their software, some of whom I believe currently perform best with CUDA.

So, the trashcan is past, they return to PCIe-slots? Interesting...

2018 15" MBP & 2015 13" MBP connected to RTX2080Ti GTX1080Ti GTX1080 Vega56 RX580 R9-290 GTX680


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Ningauble77
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Jun 4, 2019 5:49 am  
Posted by: goalque
Posted by: Ningauble77

but semi-proprietary auxiliary connectors on the Graphics Cards to feed DisplayPort from the slots to the TB3 ports and may not even work with generic off-the-shelf GPUs.

No word about standard graphics cards. I was wondering if you can combine:

"Up to 300W auxiliary power via two 8-pin connectors"

and

"Three full-length PCI Express gen 3 slots
One x16 slot; two x8 slots
75W auxiliary power available"

I just noticed those 8-pin connectors mentioned on the tech specs page... in the presentation it kinda looked like the additional power and tb3 displayport connectors were part of the slot.  I guess we will find out soon enough.

2018 13 Macbook Pro + Core v2 + Radeon VII Win10 1809/MacOS 10.14.5 Beta
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joevt
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Jun 4, 2019 5:49 am  
Posted by: goalque
Posted by: Ningauble77

but semi-proprietary auxiliary connectors on the Graphics Cards to feed DisplayPort from the slots to the TB3 ports and may not even work with generic off-the-shelf GPUs.

No word about standard graphics cards. I was wondering if you can combine:

"Up to 300W auxiliary power via two 8-pin connectors"

and

"Three full-length PCI Express gen 3 slots
One x16 slot; two x8 slots
75W auxiliary power available"

I think the tech specs say there's four 8 pin connectors (two per MPX bay). This is listed as an alternative, if you don't use an MPX module, which implies using standard graphics cards is an option.

Too bad they don't offer a Thunderbolt routing option for standard graphics cards. A third party could maybe create an adapter that exposes the DisplayPort paths of the MPX connector.

The slots are (from the top):

  • Single wide:
    • 8: x4
    • 7: x8
    • 6: x8
    • 5: x16
  • Double wide:
    • MPX Bay 2:
      • 4: x16 double
      • 3: x16 double
    • MPX Bay 1:
      • 2: x8 double
      • 1: x16 double

This picture is probably the connectors for the PCIe power cables.

PCIe power connectors

For slots 5 to 8, it appears to be one 6 pin (75W).
For slots 1 to 4, there appears to be four 8 pin (150W each).
I don't think these are used by the MPX modules. They get 475W from the MPX slot and 75W from the PCIe slot.

I don't see how DisplayPort gets to the I/O card. Are the signals in the PCIe slot? How can that be? That I/O card slot is obviously a propriety non-standard PCIe slot.

I:O card slot

The I/O card slot appears to block cards longer than x8 (there's a key in the middle). The visible lower x8 pins (fingers? contacts?) are formed to contact both sides of a standard PCIe card edge. The upper x8 part of the slot doesn't have visible pins, or they are arranged differently than PCIe pins. These are probably USB and DisplayPort signals. The USB probably comes from the chipset, so that the I/O card doesn't need a bridge chip to support a USB controller and a Thunderbolt controller. Probably the Thunderbolt controller is on the card. The proprietary I/O card slot may indicate that the I/O card cannot fit in a standard PCIe slot.

The two 10Gb Ethernet ports are down by the power plug and not part of the I/O card (the tech specs should format that text better to make it more clear).

Ethernet ports

With the I/O card, there are four Thunderbolt 3 ports (two on the top of the case, and two on the I/O card). This means there are two controllers which can take two DisplayPort signals each (four total). But the AMD Radeon Vega II MPX Module only supplies two DisplayPort signals. Does this mean two of the Thunderbolt ports cannot do DisplayPort when you only have that MPX Module? Or is there an internal MUX like in the Mac Mini 2018 that routes two DisplayPort signals to the four DisplayPort inputs of the two Thunderbolt controllers?

There is no mention of what the two SATA ports, USB port, and 10 pin plug are for.

Internal ports

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Eightarmedpet
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OliverB
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Jun 4, 2019 7:03 am  

The price is within the to be expected boundaries. No news here.
1.5 TB RAM may be enough for image processing.

In the video they say something like "with two MPX Modules (can) create the world's most powerful graphics card". What exactly is this most powerful graphics card? It's not supposed to be the RX580, the only one I can find on that site.

Edit: If found it here.
"There will also be a version with two Radeon Pro Vega II GPUs, which Apple called "the world's most powerful graphics card."

This post was modified 2 weeks ago

2018 15" MBP & 2015 13" MBP connected to RTX2080Ti GTX1080Ti GTX1080 Vega56 RX580 R9-290 GTX680


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joevt
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Jun 4, 2019 1:04 pm  
Posted by: theitsage

Above is my guess of the PCI Express lane allocation to each slot. The CPU has 64 lanes so a PCIe switch is likely hosting slot 5 to 8. The MPX with its use of a modified/extended slot is pretty cool. From what I gathered Apple routed the two Thunderbolt 3 controllers on the MPX graphics card to a x8 PCIe connection. In a fully configured Mac Pro, there are 6x TB3 controllers and 12x TB3 ports.

Slot 4 is x16. I agree that it is probably not usable when MPX bay 2 x8 connector is used.

But the tech spec imply Slot 2 is usable when MPX bay 1 x8 connector is used. The AMD Radeon Pro 580X Module is only half the width of the AMD Radeon Pro Vega II Modules and thus allows using slot 2 when installed in slot 1. This is probably why  slot 2 is x8 instead of x16.

If all 64 lanes are used by slots 1 to 4 then where do the lanes for the other slots come from? Is it possible the Apple quote of "64 lanes" for the processor also includes lanes from the PCH? The lanes from a PCH would only be good for x4 slots. Therefore, there should be a switch chip somewhere.

About the x8 MPX slots:
The MPX slots have eight lanes for two Thunderbolt 3 controllers. They are probably configured as separate x4 links so that no extra switch is required. It might be interesting if those slots supported an x8 mode for future MPX modules. That would mean the slots support bifurcation.

About the AMD Radeon Pro 580X:
It says it supports two 5K displays. That might only refer to the dual DisplayPort 1.2 variety of 5K (10 bpc) display. It might support four 5K 16:9 (8 bpc) DisplayPort 1.4 displays or four 5K2K 21:9 (10 bpc) ultra wide DisplayPort 1.4 displays.

About the AMD Radeon Pro Vega II:
Four Thunderbolt 3 ports (four DisplayPort connections), one HDMI 2.0 port, and two DisplayPort connections routed to the system means 7 outputs, but Radeon cards only support 6. There's a MUX somewhere in there to disable an output when another output is used.
It says three 5K displays can be used simultaneously. That probably means LG UltraFine 5K (dual displayPort 1.2), one per Thunderbolt controller (two from the card and one from the system).
It says only two 6K displays can be used simultaneously. Does that mean one of the Thunderbolt controllers is Alpine Ridge, or doesn't support DisplayPort 1.4? Or does it mean the Vega II can't output that many pixels?

About the AMD Radeon Pro Vega II Duo:
The picture shows what's probably a PCIe switch chip (next to the x16 PCIe connector) which supports connecting two GPUs to a single slot. It's probably a 48 lane switch with 16 lane upstream and two 16 lane downstream links.
There are two GPUs, each can support 6 displays, but it only support 8 displays. I guess Apple didn't want to add two more Thunderbolt controllers and/or four more ports, because they take space and reduce air flow (and Thunderbolt controllers take more power).
Four Thunderbolt 3 ports (four DisplayPort connections), one HDMI 2.0 port, and four DisplayPort connections routed to the system means 9 outputs. That should be doable with two GPUs, but maybe they used the same MUX as the non-Duo.
The note about three 5K for the non-Duo applies for the Duo (in this case, four 5K). Possibly eight DisplayPort 1.4 8 bpc displays might be supported.
The Duo supports the same number of 6K as 5K, possibly because two are powered by each GPU, so the note about only two 6K being supported for the non-Duo doesn't apply.

About using two MPX modules:
There are only two Thunderbolt 3 controllers on the system which can accept up to four DisplayPort connections from MPX modules. An MPX module can have two or four DisplayPort connections. If you connect two modules, which DisplayPort connections are used?
The Vega II (non-duo) module only has two DisplayPort connections. If you connect two of those modules, do you get four DisplayPort connections, or only two?

About the Apple Pro Display XDR 6K display:
6016 x 3384 60 Hz 10 bpc requires more bandwidth than DisplayPort 1.4 (1289.81 MHz required, 864 MHz available) or dual DisplayPort 1.2 (661.56 MHz required, 576 MHz available) can support. Therefore, it either uses DisplayPort 1.4 with Display Stream Compression (DSC), or it uses dual DisplayPort 1.4 over Thunderbolt (36.6 Gbps). It's probably dual DisplayPort 1.4 (like the Dell 8K 8bpc display), since the 6K display does not include a second Thunderbolt 3 port (the second Thunderbolt 3 port is used internally to extract the second DisplayPort 1.4 signal). The 6K might work with dual DisplayPort 1.2 at 8 bpc (720 MHz available) but not single DisplayPort 1.4 8 bpc (1080 MHz available).

MHz (pixel clock timing) calculated using CVT-RB. Available MHz calculated using max DisplayPort bandwidths, assuming no overhead other than that bits are transferred during blanking periods at the same rate as active periods. The pixel clock timing for Dual DisplayPort is for a single 3008 x 3384 60 Hz signal using CVT-RB. Thunderbolt bandwidth calculation assumes no blanking period pixels are transmitted (otherwise, Thunderbolt max of 40 Gbps would be exceeded).

36.6 Gbps doesn't leave a lot of room for I/O, so the display only has three USB 2.0 ports ( (type-C connector). How many USB 2.0 devices use type-C connectors? None or very few, but the USB-C ports are prettier next to the Thunderbolt 3 port, and they allow for more power for charging. The tech specs say "For Mac models with Thunderbolt 3 driving Pro Display XDR at 5K resolution, USB-C ports have USB 3.1 Gen 1 data transfer speeds."

I wonder if 5K on the XDR uses Dual DisplayPort 1.2 mode like the UltraFine 5K (10 bpc) or single DisplayPort 1.4 mode (8 bpc without DSC). Probably the former because 10 bpc is more desirable and I think Apple is referring to Macs that don't have DisplayPort 1.4 and Titan Ridge.

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joevt
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Jun 4, 2019 4:07 pm  

Since the Apple Pro Display XDR 6K display uses a Titan Ridge controller, I wonder if it has any USB-C DisplayPort alt mode input modes? They specifically mention the "upstream port for the Mac Pro and other Thunderbolt 3 hosts" which leaves out USB-C (not Thunderbolt) hosts such as the MacBook, iPad Pro, etc.

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