[EVO 4G Q&A, Help & Troubleshooting] BobWalker:
Re: EVO-4G stuck in boot loop, HELP!

Good to hear your EVO is working again Tony. When the bootloader is unlocked and a custom recovery is installed, as it is on your EVO, the phone is rooted and you are able to flash any ROM for the HTC EVO 4G. S-ON is a security flag that prevents overwriting the firmware for the radios and portions of the NAND flash. In order to upgrade the phones radio firmware, this flag must be set to S-OFF.

In your EVO's current state, you can flash any custom ROM coded for the HTC EVO 4G. There are some issues, however, related to drivers for the cameras and WiMax (4G) radio on the EVO 4G for newer Android releases. The availability of working drivers for the EVO 4G hardware along with limited internal memory are the primary factors in determining what versions of Android will work on this phone. Generally, Gingerbread (Android 2.3.x) ROMs support all hardware for the EVO 4G; but Ice Cream Sandwich (Android 4.0.x) and Jelly Bean (Android 4.1.x) ROMs do not support FFC (front facing camera) or WiMax (4G) and some ROMs may also have issues with WiFi and camera performance.

If you rely heavily on either WiMax or camera capabilities for the phone, you will want to concentrate on one of the many Gingerbread (Android 2.3.x) ROMs available for the EVO 4G. On the other hand, if you seldom use WiMax (4G) and do not need the front facing camera, there are a number of custom ROMs available based on Ice Cream Sandwich (Android 4.0.x) and Jelly Bean (Android 4.1.x). Another consideration for the selection of a custom ROM for your EVO is whether you strongly prefer a Sense based ROM similar to the stock Sprint ROM or the freedom of an AOSP (Android Open Source Project) based ROM. In general, Sense based ROMs tend to occupy more space in the EVO's internal memory while AOSP based ROMs tend to take up somewhat less internal memory and perform better.

Most ROMs available for the EVO 4G are listed at http://evo4g.roms-db.com/all-builds/ with links to the xda-developers page for each ROM. Before you undertake experimenting with various ROMs for your EVO 4G, I recommend that you replace ClockworkMod Recovery with Smelkusmod which has a reputation for wiping memory more reliably which is crucial to flashing ROMs successfully. Smelkusmod Recovery is available at http://xdaforums.com/showthread.php?t=1661543 and is easily installed by copying the downloaded zip file to the root directory of the EVO's sdcard, renaming the file PC36IMG.zip, rebooting the EVO into recovery, allowing the bootloader to detect PC36IMG.zip, and confirming the installation of the new recovery module. Once you have installed Smelkusmod Recovery, the file PC36IMG.zip should be removed from the sdcard.

In addition, you will need to consider partitioning the sdcard before installing most Ice Cream Sandwich (Android 4.0.x) and Jelly Bean (Android 4.1.x) ROMs as a number of these ROMs will not install properly without an sd-ext partition formatted with ext3 or ext4 file systems. You can read an explanation of sdcard partitioning at http://xdaforums.com/showthread.php?t=1158993. If you opt to partition your sdcard, do not forget to copy the entire contents of the sdcard to an empty folder on your computer first since partitioning will destroy all data on the sdcard! I recommend either a 512 MB extended partition (sd-ext) for 8GB sdcard or 1024 MB extended partition for 32 GB sdcard and formatting the sd-ext partition with the ext3 file system as this configuration will work with Gingerbread as well as ICS and JellyBean ROMs. Once you have partitioned and formatted the sdcard, copy the original contents of the sdcard from your computer to the newly formatted sdcard.