If I'm reading things right, the S15 uses a 72-chip single string per board. That's why the PSU runs around 19V but would only need to source ~25A per phase (assuming it uses separate rails per board, which is best for per-board tuning but also unlikely given Bitmain's cheap-out design philosophy).
You can still do a board-level regulator with narrow strings and get decent efficiency (95-97% conversion) depending on the Vin/Vout ratio and most importantly the current draw.
S9 with a 3-wide string was asking close to 50A from a single phase, and resistive losses in FETs and copper are proportional to current squared, so by shifting to a two-phase design one could halve those losses. But Bitmain likes to build cheap and sell high and cares less about longevity so that never happened.
Dedicated PSU can give you a 5-10% efficiency boost depending on what implementation you're replacing, but it also comes at a cost - you're now locked in to their hardware and their replacement mechanism.
This is key. I have a t17 and a s17 either one can use the psu included. But those are dead if the psu dies and they do not sell replacement psu’s so if you burn the psu you lose 50th for about a month.
I have been getting Whatsminer gear more then bitmain because I was able to buy psu’s as spares.
What good is the most efficient gear in the world (s17?)
If you can not get spare parts for it?
Now project to a
H P H
H P H
S21. Say 25 watts a th and 120th. If the controller or the psu dies. You have 120Th dead in the water.
Not to mention shipping it would be hard as it would weigh quite a bit.
The s17 is a good design.
They simply need to sell spare parts for it.
If I could get 10 s17 units with 3 spare psu and 2 spare controller I would get them.
But they do not sell like that.
