Upon investigating the classical Raspberry Pi Boot Block upgrade guide for Z620, I stumbled upon a software only method (ME “MANUFACTURING MODE”) to make the full BIOS chip writable! This enables easy Boot Block upgrade, and also flashing modded BIOSes without any hardware equipment.
I daisy chained a few BIOS updates together, and it bricked my Z620. So I need to be more careful with my BIOS mods. Since unbricking via a Raspberry Pi I ran my workflow again, and it worked consistently. The key is to ensure that ME is restored to the fully working version, and the “MANUFACTURING MODE” is gone upon reboot. Then the BIOS jumper recovery should work if the BIOS flash is bad.
A guide and collection of resources on how to flash 2013 BootBlock and modded BIOS to HP Z420, Z620, and Z820. The flashing procedure is done with software only, and no BIOS chip clips or desoldering. The modded BIOS supports NVME boot, ReSizable Bar, a range of CPU microcodes.
I created a GitHub project here to store all the required files: