On power-up the DEL key takes you into the BIOS. If you're prompted for a password the old Wyse password of Fireport still works on these modern thin clients.
The Wyse Zx0Q BIOS identifies itself as Phoenix SecureCore Technology Setup
My unit was running version 2.0E dated 09/07/2015.
Under the Advanced tab you can set 'Boot from USB' to 'enabled' or 'disabled' and the 'Boot Mode' to 'Legacy', 'UEFI' or 'both'.
In the example below I had a SanDisk USB flash drive plugged in, 'Boot From USB' enabled and 'Boot Mode' set to 'Legacy'.
The Boot Tab listed:
Boot Priority Order 1. USB HDD: SanDisk Cruzer Blade 2. PXE LAN: Realtek PXE B02 D00 3. SATA 0: 32GB SATA Flash Drive 4. SATA 1: 5. ATAPI CD: 6. USB FDC: 7. USB CDROM: 8: CLOUD DESKTOP: Realtek PXE B02 D00
You can also bring up a one-time boot menu without fiddling with the BIOS settings:
This brings up the Boot Menu. In my case it showed:
1. USB HDD:SanDisk Cruzer Blade 2. PXE LAN: Realtek PXE B02 D00 3. SATA 0: 32GB SATA Flash Drive 4: CLOUD DESKTOP: Realtek PXE B02 D00
The cursor up and cursor down keys let you pick what you want to boot.
The Tab key switches you between the Boot menu and the App menu. In my case there is just one entry in the App menu - Setup - which is the standard BIOS Setup utility.
A 2022 visit to the DELL support pages showed a BIOS update for the 5020 and the 7020 from July 2019. This was a 7MB download and, after expanding, included an 8MB bios.img file. i.e. The BIOS update was delivered as a straight forward binary image and so didn't need any proprietary programming tool to install it. I used flashrom V1.2 to write it. This advanced the BIOS to V2.0G 02/11/2019.