[HTC Sensation] ganeshp:
I'll try to explain stuff briefly ..hoping that it will solve other confusions too :)

well here it goes ...

1. First...Sensation by default is completely locked device (internal memory is locked )..so to either root the phone or run a custom rom ..you need to first unlock it.

2. Remember rooting the device and running custom rom are different

rooting: by doing this you will have complete control of the rom you are running be it stock or custom rom (its like administrative privileges in WIndows 7)

custom rom: this is changing the rom itself (like changing the OS From windows 7 to linux on PC )...and all custom roms comes pre rooted ..so once you flash/install a custom rom no need to root it again :)

3. Now The unlock procedure can be done in two different ways

3.1. HTC-DEV unlock : a process provided by HTC itself to support rooting of devices and running custom roms

(its a semi unlock...confused? will explain the difference later ..read on )

3.2. S-OFF: it means Security-off ..which implies unlocking the device completely (complete internal memory is unlocked)

S-OFF in turn has couple of ways to achieve it

3.2.1 S-OFF using revolutionary...It will only work on old bootloaders ..i.e. upto 1.18 HBOOT/BOOTLOADER (to put it simply it's for the sensation devices on gingerbread version of Android I.e. 2.3 version)

3.2.2 S-OFF using juopunutbear ..it will unlock even the current hboots (1.27/1.29 etc etc) (this method is primarily for sensation devices on ICS version of Android I.e. 4.0)

This juopunutbear inturn has two more ways

3.2.2.1. using juopunutbear after doing HTC-DEV unlock ..this process wipes the phone (because of HTC-DEV unlock) but the wire-trick (most imp step) is easier

(why juopunutbear ..if you already unlocked your device using HTC-DEV ? ..explained later ..read on )

3.2.2.2. using juopunutbear without HTC-DEV unlock required ..this process is harder at wire-trick part (comparatively)​

4. Difference between HTC-DEV unlock and S-OFF:

to explain this ..I'll try to give a pictorial representation of Sensation Device

Sensation as a whole has different partitions (or blocks ) ..so the whole device can be divided like this

Recovery --------firmware--------ROM (or OS)

Recovery: its a recovery mode ..the name says it all ..we change/tweak/modify rom from here ..(remember only ROM ..not firmware)

eg: stock recovery, 4EXT recovery, CWM recovery, TWRP recovery etc etc (the later 3 are custom recoveries for flashing

custom roms :)

Firmware: all the lowest level stuff comes here ...typically bootloader, radio etc etc

we flash/install Recovery and stock ROMS from bootloader.

stock roms are ..called RUU's (Rom Update Utility) and are provided by HTC ...they are in .exe format and the actual stock ROMS are extracted from the RUU which will be in "img" format

ROMS: the actual custom/stock rom comes here ..this typically has three partitions/areas

1. data partition: all your apps/app data and all the phone data you eneter goes here

when you factory reset your device this partition is erased so that phone gets resetted to factory state :)

2. system partition: all the system apps and system stuff will lie here

(in case of carrier locked Sensation ..like T-Mobile all the T-Mobile junk apps reside here)

this area is locked in general ..rooting typically means getting this region unlocked ..so that you can change

anything in the rom :)

3. boot partition: your kernel lies here along with other stuff (this region is responsible for the phone to boot)​

Now it should be obvious that Radio aka a part of Firmware wont be there in a custom ROM :) and typical custom roms comes in zip format

Now HTC-DEV process only unlocks Recovery and ROM partitions (which are more than enough for installing custom roms or rooting)

This way of unlocking is safer as tinkering with Firmware is not really needed and if mistakes were made in changing the firmware the device can get bricked permanently.

but SOFF provides unlock on every partition of the Device ..thus complete unlock..thus more ease also more risks :)

Now the big question -> why SOFF needed if HTC-DEV is safer ?

Reasons:

1. Firmware and Rom partitions are dependent ..to be more clear

Ginger Bread (GB) firmware (1.17 firmware) ..supports only GB roms ...ICS or above roms wont boot

and

ICS firmware(3.32/3.33 firmware) ...supports only ICS and above ROMS (Jelly Bean(JB) roms are supported too )

thus if you do HTC-DEV unlock when on Ginger Bread you can only boot GB custom roms as you can't change/modify firmware over HTC-DEV unlock.

if you did HTC-DEV unlock over ICS rom..you are good to go with all the latest ICS/JB custom roms

2. Flashing/installing ROM from custom recovery with HTC-DEV unlock...requires an extra step...and if that extra step is not done ..phone wont boot (literally around 90% threads in Q&A section are about this problem as people didn't knew about the extra step )

3. some people require a change in radio ..to improve phone/data signal which isn't possible if you did just HTC-DEV unlock (as radio is part of firmware )​

Another question that might come to your mind... What is the advantage of rooting the device on stock rom ..before installing a custom rom?

Answer:

people might say ..why root the device before installing custom rom when the custom rom comes pre-rooted

well here is the answer ..."to backup your phone and its data"

Remember this when installing a custom rom ..you need to wipe the phone(all the internal memory ..sdcard wiping is not needed) ..thus you will lose all data

but before wiping if you root the phone..you can backup all the user apps and its data ..also call logs, messages/MMS, wifi access points, bluetooth pairings. contatcs etc etc to your sdcard using a root app (an app which requires root permission to work ) ...and once you install the custom rom ..you can restore all the backup

..(makes things easier ..isn't it ? :) )​

5. Miscellaneous terms:

Supercid:

CID -> carrier identification ..its a 8 characterterm used in the device to identify the proper Firmware or stock rom (RUU ..remember?)

as sensation is a global device ..there are different variants of firmware and stock Roms which are uniquely identified by this cid ..

eg: T-Mobile US locked sensation has CID: T-MOBO10, europe unbranded sensation has cid HTC__001 etc etc

so when flashing firmware/stock rom ..you need to find the proper one based on your phone cid ....

but if you do a supercid (i.e changing CID to 11111111) ..you can flash any firmware/stock rom (in form of RUU )

supercid can only be done ..over SOFF and wont/might not work over HTC-DEV unlock

also now there are Universal Firmwares ..aka Firmwares which can be flashed over ( SOFF) device having any CID ..thus Supercid is now kinda obsolete :)

hoping that things are clear now ..

few threads that are much detailed

1. "flashing roms while SON" by askickar in sensation general section ...(which explains flashing rom with just HTC-DEV unlock together with the extra step needed (remember ?) )..thread here

2. SOFF process threads ...for soff with HTC-DEV unlock ..thread here

3. SOFF without HTC-DEV unlock ...look in my signature for the thread ;)

4. General way of flashing ROMS with Firmware flashing ..with ARHD Rom as reference...by joaquinf ..thread here

Happy flashing :)