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Question CSC question- Currently SIN and need to use with Tmobile or Verizon in USA

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Oct 18, 2013
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Hi all. I have the a few sm-g998b phones, rooted with magisk, and I am a bit confused about which CSC I should flash to the device (SAMKEY). I ordered the phones from Singapore and need them be more compatible with USA verizon and USA tmobile. Only using one sim per phone. Which CSC should I replace the current SIN csc with for each, and is there anything else I can do to make these phones play a bit nicer in the USA? I am currently having issues with no 5g, poor wifi calling, no updates, etc.
 

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1. Avoid SamKEY. Do your own work.
2. Flash the HOME_CSC, or the CSC of the firmware of the carrier. HOME is usually a safer bet though.
You're going to have issues in the US until you flash the proper CSC. AFAIK, every S21U has all radios, but the CSC activates the correct one.

For the absolute safest, download the TMOB stock firm, and flash the HOME_CSC (as well as the BL, AP, etc), then put the Tmob SIM in after boot.
 

varcor

Senior Member
Jul 15, 2017
569
173
San Diego
1. Avoid SamKEY. Do your own work.
2. Flash the HOME_CSC, or the CSC of the firmware of the carrier. HOME is usually a safer bet though.
You're going to have issues in the US until you flash the proper CSC. AFAIK, every S21U has all radios, but the CSC activates the correct one.

For the absolute safest, download the TMOB stock firm, and flash the HOME_CSC (as well as the BL, AP, etc), then put the Tmob SIM in after boot.
Tmobile or any US firmware can't be flashed on any Exynos Global device.
 

varcor

Senior Member
Jul 15, 2017
569
173
San Diego
Hi all. I have the a few sm-g998b phones, rooted with magisk, and I am a bit confused about which CSC I should flash to the device (SAMKEY). I ordered the phones from Singapore and need them be more compatible with USA verizon and USA tmobile. Only using one sim per phone. Which CSC should I replace the current SIN csc with for each, and is there anything else I can do to make these phones play a bit nicer in the USA? I am currently having issues with no 5g, poor wifi calling, no updates, etc.
Why would you aquire the Exynos Global variant knowing your service provider isn't optimized for your firmware? Did you save money? If so I hope saved a lot otherwise it was a poor choice. Your best option is keeping the stock SIN Firmware, at least you'll get timely updates. You MIGHT get Wifi Calling and VoLTE enabled but forget about 5G and Carrier Aggregation.
 
Last edited:
Oct 18, 2013
12
0
Why would you aquire the Exynos Global variant knowing your service provider isn't optimized for your firmware? Did you save money? If so I hope saved a lot otherwise it was a poor choice. Your best option is keeping the stock SIN Firmware, at least you'll get timely updates. You MIGHT get Wifi Calling and VoLTE enabled but forget about 5G and Carrier Aggregation.
Unfortunately, these phones are company. we needed root for some applications.
 

mpore14

Senior Member
Jul 25, 2012
83
14
Samsung Galaxy S21 Ultra
*don't use SAMKEY
This is a bit tricky because US is Snapdragon-based.
My best bet would be to factory reset (don't forget to backup) and flash a multi-csc Exynos ROM (OXM). This would detect the most compatible one for your US sims.

I would suggest getting the XSP for Singapore because that's the unbranded one.

Other than n71 5G band for US Cellular, I don't think you'll have much issues.
 

varcor

Senior Member
Jul 15, 2017
569
173
San Diego
*don't use SAMKEY
This is a bit tricky because US is Snapdragon-based.
My best bet would be to factory reset (don't forget to backup) and flash a multi-csc Exynos ROM (OXM). This would detect the most compatible one for your US sims.

I would suggest getting the XSP for Singapore because that's the unbranded one.

Other than n71 5G band for US Cellular, I don't think you'll have much issues.
"This would detect the most compatible one for your US sims" Nope, that's incorrect, Exynos Global variants aren't able to detect the most compatible US Networks. It's apples and oranges, there is zero integration for US devices.
 

varcor

Senior Member
Jul 15, 2017
569
173
San Diego
Thanks for correcting me. Least that's how it was for me using NZ sim on a G9980 SD variant.
The Exynos variants are Multi-CSC Devices, mainly for Europe, not for the US. The SM-G9980 isn't a Multi-CSC Device unlike some US Models, it's Dual-Sim. In Settings under Network Operators you can have the device select the "Best Network" but it isn't analyzing call features, it's only matching the network with the Active CSC (SIM Card).
 

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Bro,
On the stock phone dialer key in
*#2263#
You will see the bands the 998b supports.

Now u need to check on the networks u plan to use in the US what bands are used. Not sure what u plan to do but these exynos phones should be able to roam into the US with voice n data services. Not blazing gigabits but one should be able to roam globally with these phones.
 

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    1. Avoid SamKEY. Do your own work.
    2. Flash the HOME_CSC, or the CSC of the firmware of the carrier. HOME is usually a safer bet though.
    You're going to have issues in the US until you flash the proper CSC. AFAIK, every S21U has all radios, but the CSC activates the correct one.

    For the absolute safest, download the TMOB stock firm, and flash the HOME_CSC (as well as the BL, AP, etc), then put the Tmob SIM in after boot.