Don’t know right out of my head about the BIOS but I can look if I find an old unit to test.
3150 can be converted to so called 1150 WTOS based unit. Contact Wyse to buy a conversion kit.
the Wyse 3125 is a complete PC. You can enter the bios with F2 (i think).
The passowrd is fireport.
I’m running Debian Linux (Lenny) on it. Installed via PXE, stored on a usb drive.