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RTX 3060 eGPU via Thunderbolt 3 (Alpine Ridge): BAR1 not assigned — prefetchable memory window disabled on bridge #189

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@shane-prog-ai

Hi, I'm trying to use Claude to help me troubleshoot issues, and I think I will have better luck with help from actual humans! Here are the details that Claude assembled to describe the issue. Thanks so much, fingers crossed!

Your hardware:

MacBook Pro with Apple T2 chip
Thunderbolt 3 (Alpine Ridge DSL6340 controller)
TB4 HOME TB4 eGFX enclosure (authorized, 40Gb/s)
NVIDIA RTX 3060 Lite Hash Rate (GA106)
Ubuntu with kernel 7.0.9-1-t2-resolute
Driver nvidia-driver-595-open

The exact problem:
The Thunderbolt bridge (41:01.0 Alpine Ridge) has its prefetchable memory window completely disabled. NVIDIA BAR1 requires a prefetchable 64-bit window — without it the driver fails with BAR1 is 0M @ 0x0 on every boot.
What was already tried:

pci=realloc=on — Linux tries but reports BAR1: can't assign; no space
pci=nocrs — ignored by Apple firmware
pci=realloc=on pci=nocrs combined
thunderbolt.dynpower=0
Resizing BAR1 to 64MB via setpci
NVreg_EnableGpuFirmware=0 + NVreg_DynamicPowerManagement=0x00
Manual remove/rescan of PCIe device

What's needed:
A way to force-open a prefetchable memory window on the Alpine Ridge Thunderbolt bridge (41:01.0) so Linux can assign BAR1 to the GPU.

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