Developer AhMan has released details on how to remove the firmware check within iR Shell, which prevents the current release from running on custom firmware 3.90 M33. All that needs to be changed is a single offset in the PRX modules irshell38x.prx and irshell38xs.prx. With a hex editor, make the following changes:

irshell/bin/irshell38x.prx: offset 0×284e, 0×82 -> 0×00
irshell/bin/irshell38xs.prx: offset 0×28da, 0×82 -> 0×00

If you don’t think your hex editing skills are up to par, Mov of the iR Shell forums has provided a downloadable ZIP archive of the aforementioned PRX modules. Copy the files inside of the ZIP to the “bin” directory found within the iR Shell folder, hit replace, and you should be good to go.

Even after applying the patch, Mov notes that certain iR Shell functions will not work correctly when on 3.90 M33, so for a fully-functional iR Shell it is advised to stay on 3.80 M33 series firmware.

Download iR Shell 3.9 Patched Files

Patched iR Shell 3.9 PRXes [iR Shell]

Read more: PSP Custom Firmware 3.80 M33-2 Update, iR Shell 3.81, iR Shell 3.6 Released, iR Shell 3.9 Released, iR Shell for 5.00 M33 In Development