HP Z8 G4 System not booting with certain PCIe 1x cards installed.

[Sunhillo]

Hello HP Support,

I have a HP Z8 G4 System that is a base system and contains a single nVidia RTX4000 video card.  In this configuration the system boots normally to the BIOS and the OS (Redhat).  However when a certain type of PCIe card serial communication card with a 1x PCIe slot connection is added to the Z8 system the whole system fails to boot.  In this configuration  the Z8 fails to boot, there is no video output and there is no BIOS boot screen and no OS boot.  This serial card (1x) works in other systems so I know the card is good.  The BIOS level has been upgraded to HP60 v02.78 01/20/2022 and the issue still persists.

I have tried other PCIe cards in the Z8, like a 2 port ethernet card, and it seems to work OK.  Are there any suggestions to get the Z8 system to boot in this configuration?  Any BIOS changes or setting that may help here?

[BeemerBiker]

This is often too common and has to do with resource allocation.  I had the same problem with a Lenovo S20.    My USB3 adapter would not work in a 1x slot  but it worked in an adjacent one.  When I put in a WiFi PCIe card both boards worked fine.

Try another x1 or any other slot.

SANITY CHECK:  Look in bios and see if some PCIe slots are disabled.

[Sunhillo]

Hi BeemerBiker and thanks for the thoughtful ideas.  I have tried this card in every slot associated with CPU1 as we only have one out of two possible CPUs installed.  I have also already checked the BIOS and all PCIe slots are enabled.  I have also experimented with some of the PCIe setting to see it I could shift around the resources but nothing has worked.

I also removed the resource hungry  nVidia card and replaced it with a simple VGA card with the thought that the video card would be taking resources, but same problems with the simple video card.

I am beginning to think there is a PCIe timing or PCI Gen 1.0 compliance issue with this system. 

[BeemerBiker]

I assume you have AHCI enabled in bios.  That is usually needed.  Some motherboard that are missing AHCI include RAID which enables the same features.

[Sunhillo]

Thanks for the advice, but it appears that this BIOS does not have a  AHCI or RAID setting available.  Still stumped on this one.  The cards I have that don't work on this system are compliant to PCIe version 1.0A.  I am beginning to wonder if this HP Z8 has a compatibility issues with PCIe cards of that vintage.  Other PCIe x1 cards that I have like a USB card and various ethernet cards all operate properly.  Still not sure what this issue could be.