This document ( http://www8.hp.com/h20195/V2/GetPDF.aspx/c04798669 ) say that slot 5 is the correct slot for installing a HP Z Turbo Drive Quad Pro on a Z4 G4. I don't think that is correct. Shouldn't is be slot 3 which is a x16 slot vs slot 5 which is x8.
Also, if I go to the BIOS System Diagnostics to perform a hard drive test, it does not find the the 2 NVMe chips in the HP Z Turbo Drive Quad Pro. It seems that the behavior of the device is sproradic, sometimes visable to the bios sometime not.
Anyway, I need some help. All new Z4 and Quad Pro and having a hard time getting it to work.