I have been running my ESPRESSOBin in production since the day after I got it, with no heatsink and without issue. That said, I haven’t run any super intense workloads on it, as it is being used for NAS mostly, not computation and I compiled my kernel on a different system.
Also, just to be fair here, I do have it mounted in a case where there is plenty of airflow so this may also be why I haven’t seen the overheating issue.
I haven’t seen any overheating issues yet with my boards and I am not using any heat sink or fan. Haven’t tested under extreme workloads, but at the same time I do have it in a place where it is receiving passive cooling by fan.
Good luck to you guys figuring out something that works for you!
Sounds to me (just guessing here) like you hosed u-boot on the SPI NOR chip. You should be able to place u-boot on an sd-card and boot from it. Once in u-boot on the SDcard you should also be able to re-load u-boot on the SPI NOR (assuming this is the issue). I am not sure if they have this process documented yet, but at least writing u-boot to an SDcard should allow you to boot into an operating system.