S5L8900

This is the Application Processor shared between the iPhone, iPod touch, and the iPhone 3G. Not much is known about it through official sources.

Firmware File Formats

See this page for more information on the types of firmware files it interprets

Exploits

• Restore Mode - Firmware v1.0.2 and below
• LibTIFF - Firmware v1.1.1 and below
• Symlinks - Firmware v1.1.2 and below
• Ramdisk Exploit - Firmware v2.0b3 and below
• Pwnage 1.0 (Ramdisk + AppleImage2NORAccess)
• Diags Exploit - Firmware 2.0b5 and below
• Pwnage 2.0 (DFU + Malformed Certificate)

Boot Chain

VROM->LLB->iBoot->Kernel->System Software

One of the iPhoneLinux goals are to replace that Boot Chain after iBoot :
VROM->OpeniBoot->Linux Kernel->X Server->Window Manager

Upgrade Process

Restore mode

The common upgrade process chain is VROM->DFU->WTF->iBoot->Kernel->Ramdisk->Restore, also called restore mode.

DFU mode

See full article here. To flash an older version of the iPhone software you have to let your phone reside in DFU. In iTunes you have to press the Alt-Key (Mac) or the shift-key (Windows) when pressing 'Restore' to be able to manually chose an update file (ipsw file).

Boot Chain

VROM-->DFU