What does a factory reset not reset?

[AdrianM]

So you get a fancy new Android phone or tablet and then something goes wrong forcing you to contemplate a factory reset as advised by the last-ditch section in the user manual - accompanied by a warning such as:

Factory reset is not a step to be taken lightly. It

 

[sdrawkcab25]

So you get a fancy new Android phone or tablet and then something goes wrong forcing you to contemplate a factory reset as advised by the last-ditch section in the user manual - accompanied by a warning such as:
I would like to understand exactly what actually happens here. For instance, typically one or more Android system updates will have taken place on the device yet after the reset, the latest one will still be there. So your device is definitely not restored to the state it was in when it left the factory.

In my case I have an HTC phone that's unusable due to the HTC dialer crashing every time I try to make a call (right after 2.3.5 OTA). Factory reset and erasing the Flash has not cured it - so the problem has to be something persistent in the OS/program Flash areas.

I can't believe HTC would OTA an update that bricked the telephony on everyone's device out there, so I'm guessing the update itself is running up against something persistent in the 512Mb RAM... although I'm confused by terminology here, when it says 512Mb ROM surely that's not old-school ROM but Flash RAM that's reserved for the OS?

Anyway what more, if any, can be done to "clean" the device back to a fresh install of the current (or even previous) system?

Usually with an HTC phone you can perform a clean install of the OS by using the appropriate RUU (rom update utility) for your phone.

What phone do you have and we may be able to point you on the right direction?

Edit: nevermind I see you have a cha cha, I'll see what I can find.

Edit again : looks like the link found in this thread should be good:
http://forum.xda-developers.com/showthread.php?t=1511473

 

[pastafarian]

In basic terms, there are 2 parts of the OS that you are using, the RAM and The ROM. The RAM is the area that you effect in day to day use and is what gets erased in a factory reset. The ROM is not affected by a reset and can only be changed via specific software in the system and when it is rewritten the term used is to "flash" the rom. It's possible that something went wrong in a ROM flash. Usually, a bad flash will leave the device unusable and require an external flashing software to revive the device. The best advice is to post a question about this in your specific device section. Often, it's possible to find the current and previous rom files and manually flash the device to a stock configuration. You may also want to consider a rooted rom at this time. I found this, but be careful! Often ROMS are provider dependent, a ROM designed for Telus won't work 100% with one designed for Rogers.

Return to stock firmware HTC ChaCha - xda-developers
looking for RUU_Chacha_HTC_Europe_1.54.401.2 - xda-developers

Good luck!

 

[AdrianM]

Usually with an HTC phone you can perform a clean install of the OS by using the appropriate RUU (rom update utility) for your phone.

OK, so I'm at the base of the learning curve here. Do HTC provide a download for everything I would need to do this or is this making use of open-source contributions from the wider community?

As pastafarian descibes it, the OTA update sounds like the entire ROM was re-flashed, but that would mean the bundled apps that HTC provide would also be in the image (I've seen updated sense apps before in OTA's on my Legend before) But if the flash went badly (and there was no sign of that) surely the process would have a CRC or something that would fail to verify both OS and Apps there and then?

Has it ever been known for an OTA update to be corrupt without any kind of indication that things went wrong? Seeing as how that could throw subtle spanners into the works at any time I can't imagine such a sensitive operation not being properly verified.