During the early days of the PSP hacking scene, it was discovered that firmware 1.00 allowed unsigned code to run. While this firmware only existed on PSP-1000 models from Japan, many users imported these models to run and develop homebrew. An exploit was later discovered in firmware 1.50 that also allowed unsigned code to run. This opened up North American PSP-1000 systems for homebrew. Firmware 1.5 acted as the standard firmware for homebrew until the creation of eLoaders (which use various exploits to launch a homebrew "menu"), savegame exploits in games such as and and eventually DarkAlex's custom firmware releases, which all allowed PSPs shipped after the 1.51 update's release to run homebrew.