They don’t make exploits like that anymore. And frankly, after the 06.15 graveyard, that’s probably a good thing. Do not attempt to flash 06.15.00 onto any modern iPhone (iPhone 4 and later). The baseband contains anti-replay counters that will permanently desynchronize your device from Apple’s activation servers, resulting in an irrecoverable "No Service" brick. This feature is for historical and educational analysis only.
But for a brief, glorious year, 06.15 was the ultimate proof of concept: Custom Firmware With Baseband 6.15
The hypothesis was insane: Flash the iPad’s cellular firmware onto an iPhone. On a cold night in March 2011, the Dev Team released redsn0w 0.9.6b5 with a checkbox that read: “Install iPad baseband 06.15.00.” They don’t make exploits like that anymore
The warning text was stark: “This is irreversible for iPhone 3G. For iPhone 3GS, downgrading is impossible.” On a cold night in March 2011, the