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[Q] I9300XXELLA downgrade and other questions

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Vinceee
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Default [Q] I9300XXELLA downgrade and other questions

Hi everyone,

Before I flash a custom rom, I would like to know the answer to some questions I have.
This is the situation: I have an international galaxy s3, I9300XXELLA, with stock rom and android 4.1.2 and I'm interested in flashing the latest cyanogenmod 11 milestone.

I would make a nandroid backup first, so will I be able to just flash my nandroid of version 4.1.2 and downgrade from android version 4.4.2 to 4.1.2?
Also, if I make a nandroid of cyanogenmod 11, will I be able to just switch between the two roms like it's nothing?

Sorry if my questions are noob, but I've tried to downgrade before and I got stuck in a bootloop, I don't want to get this problem again..
And yes, I've searched google.

Any help is greatly appreciated!
 
Jumaqidi
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Quote:
Hi everyone,

Before I flash a custom rom, I would like to know the answer to some questions I have.
This is the situation: I have an international galaxy s3, I9300XXELLA, with stock rom and android 4.1.2 and I'm interested in flashing the latest cyanogenmod 11 milestone.

I would make a nandroid backup first, so will I be able to just flash my nandroid of version 4.1.2 and downgrade from android version 4.4.2 to 4.1.2?
Also, if I make a nandroid of cyanogenmod 11, will I be able to just switch between the two roms like it's nothing?

Sorry if my questions are noob, but I've tried to downgrade before and I got stuck in a bootloop, I don't want to get this problem again..
And yes, I've searched google.

Any help is greatly appreciated!
U cant switch like its nth. Whenever u go from cm11 to stock 4.1.2, u have to restore ur efs v1. Wat modem are u using atm?

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Vinceee
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Originally Posted by JellyYogurt View Post
U cant switch like its nth. Whenever u go from cm11 to stock 4.1.2, u have to restore ur efs v1. Wat modem are u using atm?

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I'm sorry isn't my modem the XXELLA I already gave?
And how do I restore my efs v1 then, and what is it?

Thanks
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thadoukuki
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JJEgan
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The above post is absolutely wrong. Custom ROMS including CM never include a modem in the RO

Wrong wrong wrong custom roms may and indeed do include a modem or even a choice of modems . Fairly obvious from reading rom descriptions .Modem: BUUGMJ3 Modem: XXUGMK6
Modem:
- XXEMG4
- BUUGMJ3
- XXUGMJ9
- XXUGMK6
- DDUGMK1
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tallman43
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Quote:
Originally Posted by Vinceee View Post
I'm sorry isn't my modem the XXELLA I already gave?
And how do I restore my efs v1 then, and what is it?

Thanks
Also do not flash any roms untill you know what efs is and how to back it up! not doing so may lead to a unusable phone read this >> http://forum.xda-developers.com/show....php?t=2393289 << and post any questions regarding efs in the thread.

(1) First rule of flashing roms BACK UP YOU EFS!!
(2) 2nd Rule of flashing roms SEE 1ST RULE!!

(3) EFS Issue look here >> http://forum.xda-developers.com/gala...uding-t2393289
(4) Rescue Firmware look here >> http://forum.xda-developers.com/show...35&postcount=6
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thadoukuki
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Quote:
Originally Posted by JJEgan View Post
The above post is absolutely wrong. Custom ROMS including CM never include a modem in the RO

Wrong wrong wrong custom roms may and indeed do include a modem or even a choice of modems . Fairly obvious from reading rom descriptions .Modem: BUUGMJ3 Modem: XXUGMK6
Modem:
- XXEMG4
- BUUGMJ3
- XXUGMJ9
- XXUGMK6
- DDUGMK1
Extract CM ROM zip and see for yourself if it includes a modem or not.

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Vinceee
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Originally Posted by tallman43 View Post
Also do not flash any roms untill you know what efs is and how to back it up! not doing so may lead to a unusable phone read this >> http://forum.xda-developers.com/show....php?t=2393289 << and post any questions regarding efs in the thread.
Okay I've read the topic about efs and IMEI, but I'm not sure if I understand everything correctly
Please correct me if I'm wrong and feel free to give extra information, this is what I think I understand:
  • Once I flash a rom that was made after the efs format change, I can't go back to a previous version of my modem on that rom.
    If I make an efs backup with CWM, I CAN restore it only if I go back to my stock android 4.1.2 (?)

But do I need to restore my efs backup on my new rom? I thought that wasn't necessary..

And another thing, I already succesfully installed a PA version AFTER the format change (I think android 4.3), and was able to go back to stock 4.1.2.. Got a bootloop but was able to fix that in recovery. The stock rom still works, never had problems with the modem what so ever, the only thing I did was restore my nandroid backup of 4.1.2, fixed the bootloop in recovery, and got a working, factory resetted 4.1.2...


So if I flash CM11, will I be able to go back to stock if I use a nandroid (and efs) backup?
Can someone give me a step by step tutorial please? (I just want to know what I have to do)
 
Jumaqidi
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Originally Posted by Vinceee View Post
I'm sorry isn't my modem the XXELLA I already gave?
And how do I restore my efs v1 then, and what is it?

Thanks
No. Modems have a number at the last. Like MG4. Etc

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Vinceee
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Originally Posted by JellyYogurt View Post
No. Modems have a number at the last. Like MG4. Etc

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Then please let me know where to find it, because I can't seem to find a code that ends in a number at 'about phone'

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