TonyMac32

Pulled out the hex editor to get a closer look at the bootloader to see if it was putting everything where it belongs, and I figured out why I can't see serial terminal, it's on UART2 in this build instead of UART1 like on the ASUS build.  So that explains that mystery.  I'm sure the sources could have told me that, but somehow the hex editor was easier to follow...  I also see references to the now-gone eMMC, so it's probably trying to boot that and hanging.
 
Can't get the build script to give me serial 1 instead of serial 2, but I did change the U-Boot source to the Rockchip Linux one, and I made an even more interesting adapter to ttyS2 and got this:
U-Boot SPL 2017.03-rc3-armbian (Mar 14 2017 - 23:21:19)  
It hung right away just like the mainline, I'm learning my way around to see if it's a device number issue, I'm still seeing the dwmmc@ff0f0000 (that's the eMMC address) popping up in the binary (less than with mainline), I haven't figured out where to turn that off if it's being passed as a parameter somewhere.
 
 

I'll set up a VM and try to build it.  Be patient, my software experience is with *much* lower level things (assembly language and firmware)
 
Igor, thanks for all the hard work!

I can confirm this, thank you for the info, on the NanoPi NEO Air I'm getting similar results testing my heat sink solution:
 
Stop monitoring using [ctrl]-[c] Time CPU load %cpu %sys %usr %nice %io %irq CPU 01:47:08: 912MHz 0.53 0% 0% 0% 0% 0% 0% 33°C 01:47:13: 240MHz 0.49 0% 0% 0% 0% 0% 0% 33°C 01:47:18: 240MHz 0.49 0% 0% 0% 0% 0% 0% 33°C 01:47:24: 240MHz 0.45 0% 0% 0% 0% 0% 0% 33°C <snip> 01:51:12: 912MHz 3.87 0% 0% 0% 0% 0% 0% 45°C 01:51:17: 912MHz 3.88 0% 0% 0% 0% 0% 0% 46°C 01:51:22: 912MHz 3.89 0% 0% 0% 0% 0% 0% 46°C 01:51:28: 912MHz 3.90 0% 0% 0% 0% 0% 0% 46°C 01:51:33: 912MHz 3.91 0% 0% 0% 0% 0% 0% 46°C 01:51:38: 912MHz 3.92 0% 0% 0% 0% 0% 0% 46°C 01:51:43: 912MHz 3.92 0% 0% 0% 0% 0% 0% 46°C 01:51:48: 912MHz 3.93 0% 0% 0% 0% 0% 0% 46°C 01:51:54: 912MHz 3.94 0% 0% 0% 0% 0% 0% 46°C 01:51:59: 912MHz 3.94 0% 0% 0% 0% 0% 0% 46°C <snip> 01:54:39: 912MHz 4.08 0% 0% 0% 0% 0% 0% 49°C At least the heatsink works, I used thermally conductive epoxy to attach a fair-sized heatsink to the CPU, that thermal pad they give is not very good. It appeared to level off at around 52 C 15 minutes in.