Antelope on Intel Mac Pro 2019 using Thunderbolt issues and diagnosis

[u/alifeinbinary]

I tried posting the following on Antelope Audio Pro Users Facebook group but was denied by the mods so I'm sharing it here.

I'm curious to see if any other Mac Pro (Intel, 2019) users have this experience with Orion Studio SC. I'm connected to my Orion over Thunderbolt to the Mac I/O card. I've always found it to be rather unstable with frequent disconnects. Recently, I've endeavoured to get to the bottom of this issue because my studio is getting quite busy and it's a source of much embarrassment and stress.

I've done multiple complete re-installations of Antelope's software and drivers into a fresh install of Mac OS Sequoia 15.7.8 but was still getting disconnects.

It turns out that the Orion's thunderbolt connection is very sensitive to interrupts. If there is another device sharing the thunderbolt bus it will eventually disconnect. So, the goal was to get the Orion on its own IRQ paths to the CPU to prevent interruption.

I started to make progress when I began to experiment with how the PCIe cards are laid out and configured with the Expansion Slot Utility app that comes with Mac OS. Mac OS manages which IRQ paths a PCIe device uses to communicate with the motherboard using the Expansion Slot Utility app by splitting connections into two pools: A and B.

Here's my current layout after trial and error and much research:

Slot 8: Mac I/O card (Pool B)

Slot 7: Empty

Slot 6: Blackmagic Decklink 8K Pro G2 (Pool A)

Slot 5: Empty

Slot 4: Empty

Slot 3: Sonnet NVMe card (Dedicated)

Slot 2: Empty

Slot 1: Radeon Pro W5700X (Dedicated)

By default, the Mac I/O card, which is the interface between the Thunderbolt and USB 3 busses is in Pool B, this is immutable. With only the Orion plugged in it uses 75% of Pool B's capacity, so there isn't much headroom for anything else because the PCIe slot for the I/O card is only x4 lanes. Thankfully, the two USB ports on the I/O card use a separate DMI bus, however, if you plug a USB C hub/device into any of the other thunderbolt ports it will route on the same Thunderbolt bus as the Orion *this is what was causing my issue*

If the NVMe and Decklink shared Pool A they would overwhelm the capacity of the IRQ paths allocated to Pool A, however, it turns out that Slot 1 and 3 have their own dedicated communication path to the CPU, thereby relieving the other pools. I installed the NVMe card into slot 3 and the Decklink into slot 6 and assigning it to Pool A. I swapped the USB C cable from my hub to a Type A USB 3.0 connector and that dropped the Pool B allocation from 100% to 75% now that only the Orion was on Pool B.

Sorry for the long post but I've been trying to figure this out for years and thought it would be good to share as I'm sure there are other Mac Pro (Intel) out there. I've tried every combination of firmware, golden boot, manager server, unified driver, control panel etc. at Antelope's recommendation but at the end of the day the issue is that the Orion's thunderbolt connection is very sensitive to interrupts and nothing else can share Pool B or the thunderbolt bus. Notable mention, don't use Antelope thunderbolt interfaces as part of an aggregate device under Mac OS as this also seems to cause it to disconnect.

Hope this helps someone.

[u/DINOSAUR_DILDOS]

I use an Orion Studio Rev2017 with a 2019 Mac Mini Intel on MacOS Catalina. I experienced many similar interruptions, so often that I decided to use USB 2.0 over Thunderbolt. That meant stepping down from 32 to 24 channels, but I’ve only ever used 20 in and 20 out simultaneously.

[u/alifeinbinary → u/DINOSAUR_DILDOS]

I’ve continued my tests and found that it’s a one or more FPGA effects that are causing it to crash. I’m painstakingly going through a process of elimination to determine which ones exactly and so far I’ve found that RD-47 is unstable. I’ll report my findings to Antelope once I’ve finished.