Helios4 can boot directly from the sata disk nr 1, without the need to switch from the SD or the eMMC.
I personally tried setting SW1 to 11100 and using u-boot-sata for Clearfog, which shares the same uSOM and the system booted regularly, obviously the system didn't recognize many devices being u-boot for another board.
I tried to compile a version of u-boot for sata trying to integrate the changes present in https://solidrun.atlassian.net/wiki/spaces/developer/pages/287212134/A38X+U-Boot in the U-boot build instruction and sources for Helios4 present in the Kobol Wiki but my skills are not sufficient for such a job.
In the binaries available for Helios4 at https://imola.armbian.com/beta/pool/main/l/linux-u-boot-helios4-current/ there are only u-boots for uart, flash and mmc.
Would it be possible to have the sata version in future releases?
Thanks in advance and for all the work done.