How to reset the BIOS on a HP Z840 Workstation

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I’ve had some spurious issues with my HP Z840 workstation recently. After transferring my data drives to a new system, the old system wouldn’t boot anymore. All fans and lights would come on, but no BIOS messages would display and the screen was dead. There were no diagnostics beeps either, which at first lead me to believe the system had completely died (just in time for my new system to be back up and running mind you – so it hasn’t let me down).

Turns out a complete BIOS reset brought my Z840 back to life, yet every time I added any additional (vintage) drives to the system, the same problem happened again. Here’s how I brought it back to life:

  • remove the power cord
  • remove all drives and other attachments, except for a known working GPU
  • remove the CMOS battery (bottom middle of the motherboard)
  • hold the CMOS reset switch for at least 5 seconds (bottom right of the mother board)
  • do not attach any drives just yet, but attach a monitor
  • plug in the power cord and wait

This should display a message related to the time and date being wrong and lets you enter the BIOS with F10. The defaults work fine to boot up the system both from USB, SSD or an M2 drive out of the box.

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