The HP Z620 QuickSpecs document v1 is dated 3/6/12, so there is a good chance you have the original 1.x BIOS that came with that early Z620 workstation. It is not until you get up into the 3.x level of Zx20 BIOS that things significantly improved. You can do better...
The very early BIOS versions needed a "step up" procedure before you could do a full leap to the latest 3.96 version. There are significant security and other improvements awaiting you. In January 2014 a **bleep**y, attached below) was released about this. The Z420 and Z620 motherboards use the same BIOS and setup-up procedure and for those two you need to get to at least BIOS 1.23 before you can jump to the latest. It is a bit different for the Z820. The HP ReadMe and .exe for that can be downloaded from HP (note the newer https security link addressing difference versus what was in the old advisory. These links still work if entered properly):
https://ftp.hp.com/pub/softpaq/sp64501-65000/sp64701.html
The HP SoftPaq .exe can be downloaded via:
https://ftp.hp.com/pub/softpaq/sp64501-65000/sp64701.exe
The old and less old BIOS versions had helper apps included, written for XP/Windows 7/ some for early W10. There was a spate of bad BIOS flashing that resulted, plus some bricks. I now only update BIOS from within BIOS and have attached how to do that in a PDF. The one brick I made was from not using this method trying to cut a corner in a rush... never again. For the xw and Zx20 series of workstations you run the SoftPaq, cancel out of it right after it runs, go into C drive to the SWSetup folder, and in there you'll find a folder named SP64701. Poke in there and find the J63_0120.BIN file. A copy is in the DOS Flash folder.
Copy that over to a FAT32 formatted smaller thumb drive at its top level. Shut down, insert the thumb drive when the box is fully shut down, cold boot into BIOS and navigate to the Flash System ROM entry to activate the flash. Let it restart if it wants and some will restart themselves a couple of times. Shut down, cold boot again, and then do the same same thing with the J61_0396.bin file you harvest the same way from the 3.96 SoftPaq (SP100222).