Link to Q&A: http://forum.xda-developers.com/show....php?t=1599401
I will answer to your question though:
* UNLOCKED BOOTLOADER = NO NCS = YES CUSTOM ROM
* LOCKED BOOTLOADER = YES NCS = NO CUSTOM ROM
It's a personal choice
Any mod can cleanup this thread a bit please?
Now back to the topic:
Nokia OSBL: Unless someone can find a flaw in the RSA verification algorithm, there's no reason to keep trying to patch it, since you cannot upload it anyway.
I wouldn't even attempt to write lumia 710's bootloader to the 800. They share cpu, and probably half of the memory regions, but if there's a single GPIO/mem address, i2c call, mddi call or whatever the thing uses to access the nand chip different on the 710 it may very well leave the phone as a brick. The fact that they share the chipset doesn't mean they use the same pins for the same things. If it were for any other thing I would understand, if you want to try it from an unlocked bootloader by overwriting EMMCBOOT.MBN, or if you want to chainload it from LK loader fine, but please be careful if you're going to try to overwrite it directly on the flash since it's too easy to break it down and end up seeing yourself going to ebay to get a JTAG adapter and tapping the test points on the mainboard to attempt to recover it.
I wish I knew enough assembler (or any at all) to understand the loader and be able to guess if there's something wrong, but the truth is I don't. I can see the functions, I can find the verification functions, but don't have a clue on how to even know if there's a problem somewhere.
I would start looking at differences between updates to try to find a hole in the OS. After all, it's Microsoft, it's not like there aren't going to be any bugs on 1412 fixed on newer versions. Since we can downgrade, it could be possible to get interop unlock from there, and THEN, attempt to rewrite the Qualcomm loader back to the flash, from within Windows.
At least that's what I think...
@ultrashot: here you have my config for OSBuilder, you see anything wrong with it?