Someone actually mentioned on the S5+ putting an inline delay device on the cable that goes to the controller so that it would intentionally power on AFTER the hash boards. I thought it was an interesting idea but he was wondering if that would violate warranty even though he wasn't modifying the device just putting another device in-between the the PSU and the connection. I personally think that should have been part of the controller design ANYWAY through firmware, by hey that's me. It just seemed a bit assinine to have an intentionally separate connection that another switch had to be flipped to power on a unit.
I do not think a delay is necessary, the words in the S7 document are slightly clearer than the S5+
If you use different PSU for hash boards and control board, please make sure to power the hash boards first and the control board only after the hash boards have been powered.
The key bit being in bold and although not exactly what it says I would interpret as being that Control & Hash can be turned on simultaneously, the only NoNo being Control first, Hash second?
Rich