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ASRock X99 WS: Mod BIOS to use Thunderbolt 3 AIC in CPU-supplied PCIe 3.0 slot to avoid DMI 2.0 limit?


I wanted to extend the service of an old work horse system for storage purposes by adding Titan Ridge-Thunderbolt 3 with a Gigabyte GC-Titan Ridge add-in card.

The ASRock X99 WS was an early X99 motherboard (2014), launched prior to the first revision of Thunderbolt 3 (Alpine Ridge, 2015), so it was only validated for the use with a TB2 AIC (that works fine but I wanna have the possibility of using Titan Ridge TB3 BECAUSE :wink: ).

Unfortunately the Thunderbolt AIC is supposed to go into PCIe slot 5 that is handled by the X99 PCH meaning DMI 2.0 to the CPU and PCIe 2.0 x4 are its limits.

Also, I want to use the internal 10 SATA ports that also use the DMI 2.0 interface so I want to kick anything off of it that isn’t required to avoid traffic jams.

The GC-Titan Ridge seems to operate normally in PCIe slot 5 (only Thunderbolt is enabled with default Security Level (Unique ID)).

Here is a motherboard overview with the installed PCIe devices:

There is no UEFI setting to manually allocate a different, CPU-handled PCIe 3.0 slot to the TB AIC, the latest public UEFI version 3.50 is installed.

When switching the positions of GPU and TB3 AIC (edit: So GPU in PCH PCIe slot 5 and the TB3 AIC in slot 6), USB 3.x and TB devices work as well as connected displays via DP but ejecting/hot-plugging a device on the TB AIC causes a BSOD (WHEA_UNCORRECTABLE_HARDWARE_ERROR).

(The GPU’s only task is to display a smooth UHD-10 bit-60 Hz desktop experience so it should be the least PCIe data load-causing component in the system)

As mentioned earlier the TB3 AIC works just fine in PCIe slot 5 (PCH) including hot plugging devices.

I saw later X99 motherboards by ASUS (?) that came to market after TB3 had been released where there was an option in the UEFI to select a different PCIe slot location for the installed TB3 AIC.

Does anybody know how to modify a BIOS to achieve this?

Many moons ago I contacted ASRock’s support to get this option to move the older previously used TB2 AIC but never received any response.

Thank you very much for any assistance!

aBavarian Normie-Pleb

I may have a solution for you, swap your gpu and the thunder bolt card
Pci-e slot 5 ONLY works on 2.0
Your gpu won’t need 3.0 lanes more than likely

Yeah, that’s what’s intended and what I’ve already tried. Unfortunately this leads to a BSOD when hot-plugging devices.

(I changed that part of my initial posting to bold font)

The memory of later ASUS X99 motherboards that had been validaded for TB3 and had an option to specifiy the PCIe slot number made me think that this is required in BIOS if the TB AIC is not located in the PCH PCIe slot.

Can maybe @wendell chime in if this train of thought is correct?

Would be great of the Level1Techs community would become a part of a movment to tackle the various Thunderbolt-related issues that appear if you change stuff to unsupported configurations… :slight_smile: