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A bootcode installation tool for the TI-84 Plus CE / TI-83 Premium CE
Source: https://github.com/commandblockguy/bootswap/

This program allows you to backup and restore the calculator's bootcode. The bootcode is the first bit of code on the calculator's ROM which is responsible for installing and starting the OS. Being able to change the boot code allows you to install OSes that have been modified, and also allows you to remove the "verifying" screen present on newer calculators.

The bootcode replacement process is somewhat risky - if the bootcode is corrupted, the calculator will not be able to run its operating system or any other code. This program attempts to minimize the risk involved by providing basic error checking features that give a warning when installing a bootcode that does not match a known bootcode. It also includes a few checks that will prevent you from installing something which is obviously not a bootcode. Even if the boot code to be installed is completely valid, there is still some risk involved - installing a new boot code requires the old one to be erased. As a result, there is a short period of time (<2 seconds) where resetting the calculator would cause it to become permanently unusable. Therefore, you should NEVER RESET A CALCULATOR RUNNING BOOTSWAP WHILE IT IS DISPLAYING A "Please Wait" MESSAGE. It will generally exit that screen within 15 seconds.

Normally, the boot code is in a locked sector on the flash chip (a Winbond W29GL032C). However, due to what I assume is an oversight in the bootcode, these sectors can be unlocked with only software.

This program does not work on calculators with a hardware revision of M or higher (this can be seen on the back of the calculator), as they use an entirely different flash chip that does not accept the same commands. As the revision M's bootcode expects the other flash chip, bootcodes taken from revision M calculators will also not work on pre-revision-M calculators.

BootSwap includes an option to disable OS verification. This allows you to install operating systems that have not been signed by TI. It also significantly shortens the amount of time spent on the "Verifying OS" screen after each reset on calculators with boot code 5.3.