Bootrom

Introduction / old+new

The bootrom (called "SecureROM" by Apple) is the first significant code that runs on an iDevice. The bootrom is unwritable. Finding exploits in the bootrom level is a big achievement since Apple won't be able to fix it without a hardware revision.

Certain models, including the iPod touch 2G and iPhone 3GS, have different bootrom versions. These are most commonly referred to with the terms "old bootrom" and "new bootrom." These "new bootrom" devices were released after 9 September 2009 and have the 0x24000 Segment Overflow fixed. While the new bootrom revisions have an exploit, the exploit needs the assistance of a firmware-based exploit to achieve an untethered jailbreak.

You might also be looking for Apple's stage 2 bootloader, which also uses the "iBoot" name.

Finding bootrom version

iPod Touch 2G

If the second character of your Model Number is "B" (as in "MB533" or "PB533"), your iPod has the old bootrom. If the second character is "C" (as in "MC086" or "PC086"), your iPod has the new bootrom

iPhone 3GS

DFU Mode Method

Windows

Connect Device & Enter DFU Mode
Open Device Manager, find USB controller, subitem Apple Mobile Device USB Driver
Right-Click & click Properties
Go to Details tab & select Device Instance Path in the dropdown box
The end of the info string will show the bootrom version

Mac OS X

Connect Device & Enter DFU Mode
Go to System Profiler, and under the Hardware category, go to USB, and click on Apple Mobile Device (DFU Mode)
The end of the info string will show the bootrom version

Linux

Install gnome-device-manager and start it
Connect Device & Enter DFU Mode
Search in the left tree-view for USB Device and look at Summary -> Model until it says Apple Mobile Device (DFU Mode)
If it does go to Properties (next to Summary) and search for usb_device.serial
The end of the String will show you the bootrom version

Recovery Mode Method

If a .2 (eg. 636.66.2) is behind the iBoot Version then it contains the Newer iPhone 3GS Bootrom
Note that this method will only work with the iPhone 3GS