Repairing a Bad flash on the iPod with DFU Mode (Info about DFU mode wanted)

[BeZerker]

An iPod Nano 4G can be put in DFU [Device Firmware Update] mode (iTunes registers a crash iPod and requests to download recovery software and attempts a recovery) and while this can be used to put firmware onto an iPod, can it be used to recover from a bad flash? is the info for DFU mode in the firmware? or is it stamped into the Memory? if custom firmware is installed, is DFU mode toast?

Basically, is DFU mode stamped on the chips and unerasable? or is it within the firmware?
and can it be used to recover from a bad flash on the iPod Nano 4G (8GB)?
(If you don't know if this is true for a specific iPod model, or this model mentioned; what does your device experience tell you about where the code for DFU mode is located?)

[torne]

Pretty much all hardware that implements an actual standard USB DFU mode has it implemented in a bootrom on the main system chip, and thus it can't be damaged or changed by anything under any circumstances and should be fine to recover with always.

[BeZerker]

So, If I were to use DFU mode to update the Firmwear with a modified version of apples, If needed, I could recover from it again, using DFU mode and reflashing a clean install?

[evilnick]

What I understood from Torne's explanation is that the DFU mode is non-writeable and so would always be available to be used for recovery. However many bad flashes you care to do.

[torne]

Yes, if you know how to get into DFU mode at will on the device then you should *always* be able to do that no matter how badly you have screwed up the rest of it

[BeZerker]

Thank you guys, Any site recommendations or posts on tools and tips for some Reverse engineering, testing, and recompiling of firmwear?

(I really wish we could find the iPod's public/private key for the firmwear)