[propeller10]

I am new to all this. But I don't understand how WP custom ROMs are created when the OS is closed source.

[z33dev33l]

There really isn't any for most phones and those that do have "custom roms" are just miniscule features at best. Custom roms aren't a thing we worry about much as our OS isn't broken like android.

[propeller10]

There really isn't any for most phones and those that do have "custom roms" are just miniscule features at best. Custom roms aren't a thing we worry about much as our OS isn't broken like android.

But is it possible to create a true custom ROM and tinker with the underlying OS?

[z33dev33l]

At present, no. Anything is possible but we've made no motion towards that. Not like there's any real effort. A lot of us were previous crack flashers who came to windows phone because it provided what we needed without roms.

[Catholic Tech Geek]

Allow me to shed some light on the subject then. Basically, making a custom roms involves extracting the system files from the rom image (specifically, from the imgfs part of the rom), modifying those extracted files, and then repacking everything back in the rom image (and making sure that all the files, with changes, fit within the size constraints of the rom). In order to make everything fall into place in the rom image, the memory addresses of the modules in the rom image get modified so we don't have any memory overlaps (overlapping items are bad and can cause problems with varying severity). If you want to update the operating system in the rom image, besides changing operating files within the file system part (known as "imgfs"), you need to do a further step which involves changing files in the xip part of the rom image too.

Right now, no Windows Phone 8 devices have custom roms due to lack of available tools to handle the rom format. Various developers have made tools for certain windows phone 7 devices so that the rom image for those devices can be modified. If you are not comfortable with risking your device getting bricked, I would advise that you stay away from building custom roms. I would also like to note that flashing custom roms can void a device's warranty. Many of us in the custom rom business know how to do it from previously working with making custom rom images for windows mobile devices. You can find a wealth of information on custom roms at xda-developers.