Z440 Z640 Z840 ZTD Dual & Quad Pro BIOS Gotcha

[SDH]

I've worked a lot with the ZX40 family of workstations with the Z Turbo Drive HP PCIe cards. Those include the ZTD G1 and the better ZTD G2 (with its quality aluminum heatsink) both of which only run a single M.2 stick. I've also worked with the ZTD Dual Pro (which can run 1 or 2 M.2 sticks) and the ZTD Quad Pro (which can run 1,2,3, or 4 M.2 sticks).

My advice has been to have the latest BIOS installed, and to set the BIOS to factory defaults in prep for your OS install onto the M.2 boot drive, or before doing a big upgrade such as to the latest W11 24H2. HP advises to only have the single M.2 stick in place, and I remove any other SSD/HDD/other M.2 stick. It turns out that there can be a big BIOS gotcha. I've found that the specific ZTD slot's setting of "Auto" for bifurcation works well in the ZX G4 and ZX G5 generations of HP workstations but seems to fail reliably in the ZX40 generation. The factory default BIOS setting for that in all the above 3 generations of workstations is "Auto". Thus if you have a ZTD DP or a ZTD QP in your ZX40 workstation and set your BIOS to "Factory Defaults" then on your next boot the BIOS will have been defaulted back to Auto from what you had manually set to x2x2 (for a ZTD Dual Pro in its HP-recommended x8 slot) or x4x4x4x4 (for a ZTD Quad Pro in its HP-recommended x16 slot). This critical setting and its potential to be changed this way is easy to forget.

Bifurcation means splitting up electrical lanes in one PCIe slot to serve more than one device. Current NVMe M.2 sticks need only 4 true electrical lanes so a single x8 slot can run 2 M.2 sticks and a single x16 slot can run up to four M.2 sticks. This capability was brought to the Z440 and the Z640 by a BIOS upgrade some time ago but was provided with the Z840 on release (IIRC).

The change in bifurcation to Auto in a ZX40 with a ZTD DP or QP card carrying more than 1 M.2 stick results in the primary (boot) drive not being recognized, and a black "no boot drive" screen. If the card was instead a ZTD G1 or G2 with its single M.2 stick in place Auto will work fine. The ZTD DP normally goes into the PCIe3 x8 slot, and the ZTD QP normally goes into the bottom PCIe3 x16 slot (that is a PCIe4 slot if yours is a G5 workstation).

My take home from this is that I need to carefully reset to my standard BIOS settings before my first boot after choosing Factory Defaults, and to not forget that I have a ZTD DP or QP inside.