> One core failing to start feels like an arm reset issue. We had this in the early days. Some chips were more susceptible than others.
> The fix involved ensuring one of the stb clocks was running prior to the (synchronous) arm reset.
> So my guess was firmware, and a commit related to changing when clocks were enabled.

> But that doesn't seem to tie up with either of tests.

https://github.com/Hexxeh/rpi-firmware/issues/232



> By default in RPiOS gcc is set to generate ARMv6 compatible code so that the resulting executable will run on all models of RPi including the 0 and 1 (which don't have NEON units).
https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=280934