The best place to search for information is support.hp.com, which had great, knowledgeable HP staff posting expert answers.

HP Z620 and Z820

Z620 and Z820 BIOS

Z620 and Z820 Intel ME

HP Z640 and Z840 (M60)

Maintenance and Service Guide.

Z640 and Z840

Tips how to

Reset CMOS settings

[ ] Shut down the operating system, power off the computer and external devices, and disconnect peripheral devices.
[ ] Disconnect the AC power cord from the power outlet.
|note: The CMOS button does not clear CMOS if the power cord is connected.
[ ] Push start button till PSU clicks on and off
[ ] Open the workstation, Locate, press, and hold the CMOS button for five seconds.
|note: The button is a PCB mounted small round button between the PCIe slots and the front
[ ] Close the workstation, reconnect external devices, connect the power cord and power on the workstation.
|note: Systems turns on, then off again, then on.
[ ] The system boots to an F1 prompt and displays a message that the date/time has changed and that system options have changed.
[ ] Press F1. The system shuts down for three seconds and then powers on again.
[ ] Use the F10 (Setup) Utility to reset the date and time.

Remove CMOS CR2032 Battery

Potentially original batteries: Newsun brand

The battery may be tight and hard to remove. Unplug the workstation and discharge by pushing the power button. Remove any PCIE cards that may be in the way.

Remove the battery from the compartment using two flat miniature screwdrivers, inserting each between the battery’s edge and the compartment to the side of to the two tabs holding the battery down. The battery will jump up.

Update BIOS on Z620 and Z820

Create FreeDOS 2.1 USB drive, and add bios and other firmware directories to it (using the .tgz “softpacks” from HP).

Make sure power is stable during this process. Boot up with FreeDOS USB in any USB slot, when prompted go to startup menu [Esc] then select [F9] for boot menu, select the USB with FreeDOS, and boot FreeDOS. Then navigate (DOS commands dir; cd) to the where you have your files. Z620 and Z820 have different BIOSes. For example there will be a binary file with the BIOS named J63_0396.bin, and DOSFLASH.EXE in the same directory. Run DOSFLASH.EXE by typing it plus [Enter]. Confirm to update with [y].

Enter reboot to reboot.

An alternate method is to create an USB drive with the .bin file in root directory.

Update BIOS on Z640 and Z820

Use a freshly formatted smaller USB drive and name it anything you wish. In there at the top level create the nest of three folders. These are, top to bottom, spelled exactly this way: Hewlett-Packard\BIOS\New . Down in the bottom folder (“New”), put the .bin file you saved earlier.

Plug the thumb drive into your fully shut down Z440, Z640, or Z840 and cold boot the computer, go into BIOS and find the Update System Bios feature, and choose that. BIOS might want you to confirm. Proceed with that. Walk away for at least 10 minutes because there may be one or more auto-shutdowns and auto-restarts. You don’t want to touch anything until the upgrade is fully done. It is better to wait too long than to touch anything too early.

Fully shut down the computer, remove the thumb drive.

Update AMT ME firmware

Create FreeDOS 2.1 USB drive, and add bios and other firmware directories to it (using the .tgz “softpacks” from HP).

Boot to BIOS boot menu using [Esc] then select [System Information], and check the ME Version. Is it 7 or 8? Note it down. Example:

  • 7.x –> 7.1.91.3271
  • 8.x –> 8.1.72.3002

Make sure power is stable during this process. Boot up with FreeDOS USB in any USB slot, when prompted go to startup menu [Esc] then select [F10], select the USB with FreeDOS, and boot FreeDOS. Then navigate (DOS commands dir; cd) to the where you have your files. The firmware is the same for Z620 and Z820. For example there will be a binary file with the ME firmware named 817230~1.BIN, and FWUPDL~1.EXE in the same directory. Run FWUPDL~1.EXE by entering FWUPDL~1.EXE -F 817230~1.BIN. Confirm to update.

Enter reboot to reboot.

Less well documented tricks

Crisis Recovery Jumper BIOS Re-flash

This is an advanced and risky procedure, and there is almost no documentation. It uses a jumper on the motherboard to force a flashing of the BIOS from an attached USB drive or CD.

The USB 2.0 thumb drive should be as old and small as possible (I used a 2GB, cheap stick) to be recognized, best with an activity LED on it, but that’s not necessary. It just needs to hold the latest BIOS binary file that is found in the BIOS update software packs. Place this bin file should at the root of a FAT32 formatted drive.

Z820: The jumper E15 is between the legacy PCI slot and the first PCIe slot closest to the bottom. The default position is connecting pins 1-2, meaning the jumper is towards the rear of the case. To force flash, the jumper will be moved to 2-3 position, towards the front of the case.

This procedure worked on my Z820:

[ ] Turn off, disconnect all cords, including power cord, clear power by pushing the on/off button for a few seconds.
[ ] Move the jumper to flash position. Insert USB drive in a USB2.0 port, I used the front top port.
[ ] Connect power cord, and display cable to graphics card.
[ ] Start boot by pressing the on/off button.
|note: You will hear 8 beeps and red light on front, the system may reboot, and then boot as usual, finally showing something like "Flashing..." wait for this to complete, and system shut down.
[ ] When the system is shut down, pull the power cord
[ ] Move the jumper to default position, and remove USB drive.
[ ] Start system, Boot, and press [Esc] to go to Boot Menu. Then [F10] to Computer Setup, and select the item from the menus to reset CMOS to factory settings.

For good measure, replace the CMOS battery after you succeed, unless you are sure the battery is not old.

Official Z640 and Z680 instructions archived here.

Z640: Flash position of jumper is towards the rear of case.

Z680: Flash position of jumper is towards the front of the case.

[ ] Power off system and unplug power cable.
[ ] Remove side panel and locate "Boot Block Recovery Jumper" on side panel label.
[ ] The jumper will be on a 3 pin header where 2 of the 3 pins will be loaded by the jumper.
|note: On the Z840 load the jumper on the 2 pins towards the front of the chassis.
|note: On the Z440 and Z640 load the jumper on the 2 pins towards the rear of the chassis.
[ ] On a USB key (preferred format FAT32), with a built in LED to show activity, place the .bin file of BIOS version 2.20 or later install on the root directory.
[ ] Install the USB key onto the failing system, insert power and press power button.
[ ] When the system is powered on it should be followed by 8 beep audio code. Disregard this as this is normal behavior.
[ ] The USB key activity LED will begin to blink slowly then rapidly in most situations. This process will occur twice.
[ ] If BIOS Recovery is successful, the display will show a BIOS Recovery screen with the update in process. "Don't shut off power at this state."
[ ] When install is complete, the system will power off.
[ ] At this point unplug the power cable and USB key.
[ ] Return the Boot Block Recovery jumper to its original location. Replace side panel.
[ ] Insert power cable and press the power button. The system will come up with a black screen and shut off once, then power on by itself again and if successful the BIOS post will appear. *If recovery steps unsuccessful replace system board.

Additional references: https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/Jumpers-on-Z620-FMB-1102-motherboard/td-p/5705488 and https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/Crisis-Recovery-Jumper-Z620-Z420-Z820-Revealed/td-p/6658619

BIOS update related info

To determine the BIOS family and BIOS date, press F10 on the target workstation during Power On to run the Computer Setup Utility, and then select File/”System Information”. This information can be saved into a text file on a USB flash media device by selecting File/”Save to Removable Storage Device”.

For a USB flash media device to be recognized by the workstation, the device must be attached before the workstation is Powered On.

Boot and BIOS

Symptom: Boot Stuck at HP logo, not entering BIOS Menu, not proceeding to boot

Try resetting CMOS settings first, and perhaps the following. If all fails, you may need to try the crisis jumper BIOS re-flash method.

 ‎01-21-2019 03:14 AM – last edited on ‎04-13-2021 06:42 AM by Retired Chao_L

First:- Turn off the computer, press and hold the PWR button for 4 seconds.
Then – Leave only keyboard and mouse connected, disconnect all externally connected
devices such as Docking Station, USB storage devices, displays, and printers.
Unplug the AC adapter from the computer.
Next – Press and Hold the Power button for 15 seconds to Hard Reset.
Rinse and Repeat
AND/OR – Power on your PC, press Esc (repeatedly), then F2 at the prompt.
Choose System Tests (Fast Test does a 4 minute hardware check).
AND/OR – Windows Logo key + Ctrl + Shift + B
(This key sequence actually restarts you graphics drive(W10 only).)
AND/OR – If you’re using multiple displays, try projecting video to a different monitor.
Press the Windows Logo key + P, select a display, and then press Enter.
https://support.hp.com/us-en/document/c02693833

Turn off the computer, and then connect the power cord.
Press and hold the Windows key and the B key at the same time, and then press and hold the power button for 2 to 3 seconds.
Release the Power button but continue pressing the Windows and B keys. You might hear a series of beeps.
The HP BIOS Update screen displays and the recovery begins automatically. Follow any on-screen prompts to continue the startup to complete the recovery.
HP BIOS Update recovery in progress

If the HP BIOS Update screen does not display, repeat the previous steps but press the Windows key and the V key. If the screen still does not display, your computer might not support the feature or there is a hard drive issue. Continue to the next step to install a BIOS recovery file from the HP website.
If the Power light turns off, the Power button was held too long. Repeat the previous steps, making sure to hold the button for only 2 to 3 seconds.

https://h30434.www3.hp.com/t5/Desktop-Boot-and-Lockup/Computer-stuck-in-hp-logo/td-p/6982421

Symptom: BIOS update freeze

https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/Z820-Bricked-Bios-after-Firmware-update/td-p/5718307

Front Panel Connector Pinout

Zx20 models have the same pin-outs. The connector is the third one from the left below the legacy PCI connector, counting from the back of the workstation.

On Z640 the connector is the second one from the left.

LEDs: HP systems have LEDs connected back-to-back; blue or white (color) and red (blink.) Shorting pins 7 and 8 momentarily turn the computer on or off. The Ambient Sensor is a thermal sensor in the front panel cable. Without this, the system fans will probably ramp to full speed.

Pinout for connector P5 "FRONT UI" on the main board:
1: HDD_LED+ 2: Power_LED+ Blink
3: HDD_LED- 4: Power_LED- Color
5: GND 6: KEY/missing pin
7: Power_Button# 8: Power_Button_GND
9: Chassis_ID0 10: Chassis_ID1
11: Ambient Sensor DP 12: Ambient Sensor DN
13: Hood Sense 14: Intruder
15: Speaker Out + 16: Speaker Out -

ref: https://h30434.www3.hp.com/t5/Desktops-Archive-Read-Only/Front-panel-connector-pinout/td-p/5540808

Expansion slot numbering

The first slot is closest to the memory, and inaccessible if the system has a second CPU board installed. The slot number increases towards the bottom.

Design Flaws

Z820: The Ethernet ports are too close to a metal wall, making unplugging Ethernet connector slightly difficult without a tool.

Z820 and Z840: The CPU and memory fan assembly is audible even when the system operates at low load.

Service Manuals

http://HP Z440, Z640, and Z840 Workstation Series Maintenance and Service Guide

updated: 20240412