After getting more involved with the "aftermarket" community, I have this question that's been on my mind for a while now. Since rooting and flashing a custom ROM on an Android phone doesn't give one SIM unlock that means that the SIM lock settings must be stored somewhere else in the phone's memory.

My theory goes that the SIM lock information is stored in or along with the baseband. Is this true? And if so, are there any "alternative" or "aftermarket" baseband firmware images? And finally, who makes the baseband firmware - the carrier, or the phone manufacturer?

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    Any idea why this question was voted down? It's strange this SE site.. I wonder if it's going to actually be successful past the beta with such attitude.. – Miky Dinescu Feb 6 '11 at 22:10
  • I have no idea why. Someone liked it, someone else didn't. There are numerous discussions at meta.SO about downvoting in general but in the end, downvotes part of the system so don't take it personally. If you want to know why something was downvoted, feel free to ask like you did, although I wouldn't hold your breath for a response ;) If you'd like to discuss the strengths/weaknesses of this site or the SE system you should do so on the meta site where such discussions belong. – Matt Feb 6 '11 at 22:26
  • I suspect it's because this question would also apply to an iPhone.. eg it is not Android specific in any way – Jeff Atwood Feb 7 '11 at 6:41
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    But @Jeff, doesn't the title (and the mention of "an android phone" in the question) imply that I'm interested specifically in android devices? Of course, maybe this is common to all phones but I though that the sim-lock configuration was something stored in the phone's firmware hence android related. Of course, @Matt's answer proves me wrong. – Miky Dinescu Feb 7 '11 at 18:47

The SIM lock stuff is in a separate ROM chip that is not part of the normal phone storage, AFAIK. It's manufacturer/device dependent. Definitely nothing to do with the baseband (and you can certainly flash other basebands).

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    So my hat is in with the not-Android-specific people, but I think it's ontopic because the average Android user may wonder about this. – Matthew Read Feb 8 '11 at 18:31
  • Is there any way to display this setting? Short of installing a SIM card from another carrier, how can one determine whether an Android phone is SIM locked? – Derek Mahar Apr 19 '11 at 10:01
  • Normally there's a code you can punch into the dialer, but it's manufacturer/carrier/handset specific. – Matthew Read Apr 24 '11 at 6:46

I saw a professional in China unlocking HTC handsets via JTAG. A side effect with the unlock was the S-ON.

The SIM lock is stored in the Radio NVRAM, is not changeable, but they did the unlock by flashing a patched HBOOT with S-ON and that will report a different SIM lock status (my unlocked phone still says SIMLOCK in fastboot mode - another proof of that is that the fastboot mode now contains a Chinese URL)

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    Then your chinese unlocker flashed an hboot that ignores the security bit. – Broam Sep 21 '11 at 13:59
  • That's what i wanted to say :) – Magnetic_dud Sep 26 '11 at 9:21
  • Is HBOOT specific to HTC phones? How can I get SIM lock to be ignored for a Moto E4 (that was on Sprint) which does not even ask for a SIM unlock code? – user3236841 Jan 19 '20 at 18:24

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