Acquiring S-Off is the Holy Grail of all root for HTC device owners. With S-Off, users can flash unsigned firmware images and obtain permanent root. For those who would like to go even further, you can always flash the Engineering HBoot, or ENG HBoot for short. This offers even more fun, such as extended Fastboot commands. For many HTC owners, flashing the ENG HBoot after obtaining S-Off is a priority. This can now be done on the HTC Rezound thanks to XDA Recognized Developer con247, who has posted a thread allows users to have the ENG HBoot, with all associated perks.
As with any HBoot installation, be sure you read everything very carefully. Says con247:
If you try to S-ON the device with this HBOOT on it, it will BRICK. Restore the original hboot first via RUU.
And another warning added on by XDA Elite Recognized Developer jcase
If this is the eng hboot I posted, avoid flashing it unless you know exactly what you are doing.
It may have issues with newer ICS radios.
So if you’re running ICS radios and/or aren’t yet S-Off, do not install this. If you’ve fulfilled all the safety requirements, then the process is actually relatively simple. Download the modified PH98IMG.zip, double and triple check that the MD5sum is correct, and install via the bootloader. Once done, you have gotten the ENG HBoot.
For more details, thread discussion, screen shots and more, check out the original thread._________