Is the thunderbolt 3 GPIO cable available?

[SDH]

That card is what I have too. There have been posts here indicating that the Thunderbolt 3 firmware update(s) are included inside ZX G4 BIOS updates but not stated as such in the corresponding HP ReadMe for the BIOS update SoftPaq.

There also are posts here that comment on the ZX G4 BIOS throwing an error that it could not update the TB3 card firmware and gave the option of continue attempt (dead end) or continue boot as is. There is a BIOS option to uncheck the box by check for firmware update. I tried both ways and zero success, and that is why I think my card may not have any firmware on it to start with.

There is a recent Z4 G4 BIOS update released 1/6/25, version 02.95, with a slightly larger size for the Core motherboard than for the Xeon motherboard, and two different SoftPaq numbers (SP156541 if Core; SP156539 if Xeon).

The most recent Thunderbolt 3 HP software installer also includes mention of the ZX G5 workstation being supported but that may simply be a universal installer that knows what it is seeing physically and then batch file installs based on that from its stash of components. Physically the TB4 card for the ZX G5 workstations is quite different.