I had no clue how to title this but first the background. I have four UNO boards and six AT processors in various states of working condition. On boards #1 and #2 downloading to any of the ATs won't work. With known good ATs board #1 always gets a "USB device not recognized" from Windows(10) and on board #2 I don't even get a beep from the computer recognizing the connection. Boards #3 and #4 can connect and download perfectly in identical setup with good ATs. Don't know if it is coincidence but the good boards are newer R3 UNOs - backside is half white. Do these failure modes point to whether the first two boards are salvageable or where they failed? Cooked 16U2?
Moving on to the ATs. Using boards #3 and #4 three of the chips worked perfectly. The other three connected but when downloading they generated the same Arduino IDE errors of "programmer not responding" and "not in sync". Gone through all of the troubleshooting tips and I tried reinstalling the bootloader via these instructions using optiloader for two of the failed ATs but get:
Target power on! ...
Starting Program Mode - Failed, result = 0xFFFF
Target power OFF! (result = 0x0 for subsequent tries)
FYI - above results are consistent for either Rev 1.0.6 or Rev 1.6.7 (Will be scaling back to 1.6.5 soon but that's another story)
From the above can the future of the non-working ATs be determined (dead or not)?