I own both a Z620 and a Z820 Workstation! The Z620 updated the BIOS from 3.91 to 3.92, then 3.93, and finally to 3.94 progressively over the years with no problem! The Z820 updated from BIOS 3.91 to 3.92 producing a brick that would not boot! Thanks to Ashleigh-Paul HP Support Community 5718307 I was able to revert back to BIOS 3.91 and recover the full use of the Workstation! Curiosity may have killed the cat, but satisfaction brought it back! Not so fast! My next adventure was Bios 3.91 to BIOS 3.93! Horrors, another Brick! Using the previous Ashleigh-Paul technique I again reverted/installed Bios 3.91 and fully functioning Z820 Workstation! Surely an upgrade to BIOS 3.94 would succeed! NO, another brick result! Thank God for Ashleigh-Paul, and return to a fully functioning Z820! Then BIOS 3.95 appeared, would I take the bait and risk another defeat! Yes I fell for the allure of potential success, but sadly, crestfallen, you guessed it, Bios 3.91 to 3.95 was an utter failure! Once more Ashleigh-Paul to the rescue, restoration of Bios 3.91 and a fully functional Z820! Hope springs eternal when I recently received a message regarding this problem and a reference Advisory HP Z440, Z640 and Z840 Workstations! Fascinating, but unfortunately no Advisory for Z420, Z620 and Z820 which would be most helpful! My conclusion is that the Z820 BIOS 3.92, 3.93, 3.94, and 3.95 are corrupted since they are not compatible with my Z820! I could be mistaken, or perhaps this is one of life's mysteries which has no plausible answer!