[EVO 4G Q&A, Help & Troubleshooting] stefpap:
So since all the other threads revolving around this issue seem to be nothing more than suggestions of things to try rather than trying to determine what the problem is, I wanted to start fresh.

Here's my issue regarding reboots on my Evo (Hw 003). Simply put the phone will reboot (typically under moderate/heavy use, I've not once seen it reboot on it's own, although I can't say it hasn't when I've been asleep).

This issue has persisted regardless of HBoot Version (I've been on 0.76 ENG, 0.97, and 2.10), PRI, Radios or ROM. Trust me, I've tried nearly every combination. It even persists when fully unrooted and returned to stock.

I've obviously tried every type of wipe (both through CW and Amon's Recovery and using Calkulin's WipeAll method in both recoveries) prior to flashing roms and after restart/crashes. I've tried eliminating SD Card issues, and these issues persist regardless of whether the SD card is in or out, or whether it's corrupted or not.

Here's the only things I can definitely say regarding the reboot issue (which I do have to believe is a HW issue, although it may have something to do with the early boot sequence...see my reasoning below).

When the crash occurs, the phone ALWAYS attempts to reboot itself. Very rarely it will do this successfully (but it seems to only be successful in doing so when on customs ROMs, specifically CM7 nightlies, which makes me think that those crash/reboots are unrelated and are actually just software issues with the rom/apps in question and should therefore be disregarded).

If my phone is currently set to S-OFF, the reboots always ends with under 5 seconds on the white HTC Evo screen, then display goes black and I get five vibrates and a flashing green power LED. When this happens and the phone is connected to my laptop via USB, right after the 5 buzzes, I get a Hardware Growl notification that a Qualcomm USB device has been connected.

If the phone is currently set to S-ON, the reboots result in a bootloop that again, shows the white HTC Evo screen for less than 5 seconds, then the screen goes black, phone restarts and starts the loop again. In these cases I don't get the Qualcomm/HW Growl message.

With S-OFF the only surefire way to get a working phone back is to remove the battery for a few minutes (seems like it needs at least 3-4 minutes, which makes me think some form of volatile chip/ram needs to drain to a certain point before working again). I can always get HBOOT/FASTBOOT though, even if I just remove the battery for a second. It feels like I can get into Recovery with the battery removed for less time than it takes to actually boot into the OS, although this may be an inaccurate observation on my behalf.

With S-ON, while removing the battery seems to yield the same results as when the phone is S-OFF, occasionally if I let the bootloop play out, it will eventually hang on the white HTC Evo screen for some time, then restart and boot like normal.

---------Conclusions----------

From what I can tell this whole reboot/crash issue people seems to be having (when it isn't caused by bad flashing or improper use of the phone) can be narrowed down to two areas.

1 - There is an issue with the phone's RAM. This would make sense since there is a difference in the results of removing the battery for a short time or long time when trying to recover from a crash.

2 - It's an issue with the phone's early boot sequence. Perhaps the phone's internal memory (specifically the boot partition or wherever HBOOT/FASTBOOT is stored, not 100% sure where that actually is) has bad sectors or is otherwise corrupt.

I'm leaning towards the RAM being the culprit though, since it seems to be the only thing linking all of the different crash/reboot scenarios. And although I've heard rumblings that it may be a CPU issue, I really doubt this since I can always get into HBOOT/FASTBOOT and because when it crashes and give the 5 buzzes (which some have speculated is a Qualcomm error code for CPU's) it then seems to be communicating on some level through the CPU and USB with my laptop.

While I obviously can't replace the phone's RAM to check this, I just wanted to see what the opinion of those who are a bit more familiar with the phones inner workings than I am have to say about this.