What version(s) of the BIOS still only require the main "SPI ROM" to be patched rather than both chips and how would I determine whether my BIOS is that version?

Also how do you guys go about unlocking these BIOSs, is there a tool that you use? I've noticed that it's mostly just switching 0x3F to 0x3C in the .bin files however the newer versions seem to require more work...