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How To Guide G998U and G998U1 Firmware Links and Flashing Discussion Here

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visualpro

Member
Mar 18, 2012
39
10
Is this reflashing working for anyone? I tried to go from U1 to U TMB. Although the firmware does state it is the U firmware, the version is still XAA. Downloaded the firmware using Frija and flashed using Odin with CSC (Not HOME_CSC) and USERDATA for TMB. The CSC version remains XAA/XAA/XAA even after installing a TMB SIM card. For a U1 firmware, alt least it will try to install the CSC on its own once you insert the SIM card. Not sure I will be able to successfully go back to U1 and get at least some of the TMB functions back.

Either all the carriers have put a stop to such flashing or the firmware distributed is flawed.
I have U1 XAA.. I'm on T-Mobile network.. I was able to flash to TMB U firmware(Android 12) including the USERDATA.. Booted up with TMobile boot logo.. Saw the new eSim support as well.. It worked just like U phone.. I was able to revert back to the latest XAA firmware back (still on 11)

My CSC are TMB/TMB/XAA.. The last CSC cannot be changed. It identifies the actual type . Since mine's US unlocked it showed up TMB/TMB/XAA .. when I first got the phone it was like XAA/XAA/XAA, changed to TMB once sim was inserted. Hope this helps.
 

sultan.of.swing

Senior Member
Apr 12, 2010
1,201
120
Camas, WA
I'm confused by this post, in the original post when I click on the firmware link posted there were no files there.
Nevermind I see it.
 
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iBowToAndroid

Senior Member
Nov 9, 2010
4,899
1
1,560
Twin Cities MN
ATT USERDATA has been added for Android 12 - build UK7. All other carriers got this same version so the rest of the files are readily available elsewhere if needed
 

iBowToAndroid

Senior Member
Nov 9, 2010
4,899
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Twin Cities MN
Waiting for BUKG. Said it fixed hz lags issue
I thought UK9 was the lag fixer. There's also a UKF
I'm not getting the BUKG update on my t-mo U version. Any ideas of what might be going on? I used odin to flash BUK7.
1. T-Mobile has UKF, not UKG

2. No OTA update gets pushed to every single phone at once. That's not how OTAs work

3. You can use Odin to flash UKF just as easily as you did UK7
 
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Dstu10

Senior Member
I thought UK9 was the lag fixer. There's also a UKF

1. T-Mobile has UKF, not UKG

2. No OTA update gets pushed to every single phone at once. That's not how OTAs work

3. You can use Odin to flash UKF just as easily as you did UK7
Right I went on and used smart switch to update to UKF. Seems strange I didnt get the update. Any way to check to make sure I flashed the correct firmware?
 

Sky33

Senior Member
Oct 7, 2021
70
10
I thought UK9 was the lag fixer. There's also a UKF

1. T-Mobile has UKF, not UKG

2. No OTA update gets pushed to every single phone at once. That's not how OTAs work

3. You can use Odin to flash UKF just as easily as you did UK7
I see. I guess waiting for UKF then. UK9 didn't fix the lag for me. Some other members said UKG fixed the lags finally
 

iBowToAndroid

Senior Member
Nov 9, 2010
4,899
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Twin Cities MN
Right I went on and used smart switch to update to UKF. Seems strange I didnt get the update. Any way to check to make sure I flashed the correct firmware?
If your current Build Number and Baseband end in UKF, then yes, it was flashed correctly
I see. I guess waiting for UKF then. UK9 didn't fix the lag for me. Some other members said UKG fixed the lags finally
Why would you wait, when you can manually flash it via Odin any time you want?
 

Sky33

Senior Member
Oct 7, 2021
70
10
If your current Build Number and Baseband end in UKF, then yes, it was flashed correctly

Why would you wait, when you can manually flash it via Odin any time you want?
I couldn't find the UKF on the link you posted on the first page. Do you happen to have the link for me to download the UKF for G998U?
 

Jameszet

Member
Mar 11, 2012
26
2
39
DF
I have a g998U from ATT with current version android 11 G998USQS4AUFD and want to flash g998U1 android 12 G998U1UEU4BUK7 to get rid of bloatware and upgrade firmware

Steps followed:

1. all files loaded into ODIN (both firmware and odin downloaded from sammobile)
2. phone into download mode
3. started process in ODIN
4. got SHA256 invalid

any help here?
 
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    For those who aren't already aware, G998U is the model number of all of the US carrier versions of the S21 Ultra. The G998U1 is the model number of the same device, but sold by Samsung SIM unlocked and with no carrier bloatware. Firmware is 100% interchangeable among these models: any U or U1 firmware version can be flashed to any U or U1 device at any time, assuming that you're not trying to downgrade the bootloader. A "U to U" or "U1 to U1" flash does not require a factory reset, but changing from one firmware to the other will require one. Also, U firmware is identical for the 4 base files (AP, BL, CP, CSC) for each individual build, no matter which carrier it comes from. So if you download 2 different carrier versions of the exact same build, the 4 base files will be identical. Where the firmware differs is in the USERDATA file - that's where the carrier bloatware and customizations reside.

    Manual Odin flashing is designed for those who:

    - want to manually update to a newer version of U firmware on their U device, either because they don't want to wait for their carrier's OTA or because OTAs aren't working on their device, or a different carrier got a new feature/patch before they did
    - want to flash U1 firmware to their U device
    - want to convert from U1 firmware to carrier U firmware
    - want to convert from one carrier's U firmware (with all apps and bloatware) to a different carrier's U firmware (with all apps and bloatware)

    For those who aren't already aware, anyone can now download firmware for almost any Samsung device any time that they want, via the various firmware download tools posted here on XDA like SamFirm or Frija. There are threads and info about them here on XDA so I won't waste time explaining - do a search if you're not already familiar with these tools. But they only provide whatever the latest/newest/current version is - nothing older. I pay for a subscription to a site that gets the official releases (usually) before they hit the firmware download tools, so that's where my files come from.

    This is not a "beginner's guide to Odin flashing" -type post/thread, so I won't list basic, step-by-step flashing instructions. My threads are geared towards those who already know what they're doing. If you're new to manually flashing Samsung firmware (or haven't done it in a long time), I recommend you consult one of those "beginner's" guides- there are tons of them here on XDA.

    Happy flashing!

    U firmware: https://www.androidfilehost.com/?w=files&flid=322089
    U1 firmware: https://www.androidfilehost.com/?w=files&flid=322090

    Notes:

    - DON'T QUOTE THE OP WHEN YOU REPLY, kthx

    - I have lots of threads just like this one for other Samsung flagships, if it interests you. For those who have already made use of my previous threads for a different device and are upgrading to an S21, welcome back :)

    - My zips are compressed extra small for space and bandwidth savings. The default Windows extractor can't handle it, so you'll need a 3rd party tool like 7zip, WinRAR, etc

    - it's quite time consuming to download the files, zip them up, and upload them to AFH. And, I do threads like this for every single Sx and Note x model, so I won't be uploading every single version. The only full builds that I upload are ones where I get access to a new bootloader and/or Android version early, before they hit the firmware download tools.

    - My naming method for folders on AFH is: build - bootloader - Android version
    So "SAT - 1 - 9.0" means the full build number ends in SAT, it's bootloader version 1, and it's Android 9.0. When bootloader and Android versions increment, the first build to have those changes will have its folder notated appropriately.

    - HOME CSC file keeps data intact; using the other CSC will wipe data. Flashing USERDATA will also wipe data.

    - Since AT&T doesn't allow their firmware to be publicly available (for any of their devices), I'll try to always upload at least one USERDATA per bootloader increment for AT&T (and Cricket, if they get this model). I'll also upload any full builds if AT&T is the only carrier to get that specific build, because you won't be able to find the files anywhere else.

    - For identifying USERDATAS, and to know what region/CSC to use in the firmware download tools if you're downloading yourself:

    AIO = Cricket (not available via firmware download tools)
    ATT = AT&T (not available via firmware download tools)
    BST = Boost Mobile
    CCT = Xfinity Mobile (Comcast)
    CHA = Spectrum Mobile (Charter)
    DSH = Dish Network
    SPR = Sprint
    TMB = T-Mobile
    TMK = Metro PCS
    USC = US Cellular
    VZW = Verizon (available via firmware download tools, but Manual Entry is required - Auto will not work)
    XAA = U1 firmware

    - the correct procedure for switching from one carrier's firmware to another carrier's firmware is:
    1. Flash full U1 firmware package including non HOME CSC
    2. Upon boot, insert a SIM of the carrier whose firmware you want
    3. Watch for the popup that says "reboot to apply new carrier settings" etc, and do it
    4. After that restart completes, reboot back to Download mode and flash the full U firmware package, with the USERDATA file of the carrier whose firmware you want
    2
    Initial U firmware and AT&T USERDATA are posted, along with U1 firmware. U firmware is not yet accessible in the firmware download tools like SamFirm and Frija, but if anyone wants a different carrier's USERDATA (for flashing bloatware to a U1 device or for converting a U device from one carrier's bloatware to a different one), let me know and I'll get it for you
    2
    I've seen nothing about the May update for the G998U1. Older phones are getting it but we haven't.
    2
    Have the Verizon version, what is the benefits of flashing to U1?
    The only benefits I can think of would be enabling Samsung features that Verizon disables, like the Spam Filter, and removing some of the bloat that might be impossible to remove on the VZ version.
    2
    I would think you would have most features since the U1 firmware is sold by Samsung to work on networks like T-Mobile. However, all I can verify for you is that I got my wifi calling and I have a 5G icon with 305Mb on speed test. This is after flashing U1.

    I had the same issue. Out of the box, without even turning the phone on, I flashed the U1 firmware on my T-mobile S21 ultra but the device just kept saying "NO SIM"

    If you have a T-mobile device, turn it on with an active sim card first with the original U firmware. Don't need to go through the setup, just have to let it find a LTE/5G signal. After that you can power down and flash U1 firmware and won't have any SIM issues.

    Hope this might help anyone who might run into the same issues we did