Multifw v1.2.6

Flash only one file: pg-multi.uf2 only one time. It contains all firmwares (6 at this moment). You can change between them in DOS:

New usage for this version:

pgusinit   /m x [d]  - change card mode to x (1=gus,2=sb,3=mpu,4=tandy,5=cms,6=joy)
           the optional parameter 'd' makes the mode permanent at boot
           (Only if pg-multi.uf2 is flashed)

Examples of use:

You have default mode as GUS mode on boot, want to change mode to SB, but only temporarily:

pgusinit /m 2

You want to change the default (permanent) mode of the card to SB mode, and the next system cold boots / hard resets / power off you want to stay in SB mode without using pgusinit:

pgusinit /m 2 d

Thanks to @polpo for the main code and @jeroentaverne for the great code of pico multiboot here!!: https://github.com/jeroentaverne/pico_multi_firmware