Johnny B Good wrote:
If any of those power rails are eventually to become obsoleted, it's
more likely to be the +5 and +3,3 volt rails, That "Legacy +12v line"
will most likely become the 'defacto' standard for distributing DC power
to everything in PCs and IT kit in general simply because of the ease by
which the actual chip voltages required can be generated by commodity on-
board dc-dc switching regulator chips.

This is already the case. Many servers are 12V only, or only have a small
amount of current on 5V rails. Graphics power supplies are also 12V only -
they have 3.3V from the PCIe connector but only at limited current.

However the countervailing force is USB, which encourages 5V usage.
It remains to be seen whether USB C will usher in common use of higher
voltage USB (it'll go up to 20V).

I think we'll see 12V for bulk power, and USB Power Delivery up to 60W (12V
@ 5A), with 100W PD (20V @ 5A) reserved for more specialised
chargers/docking stations. 5V will persist for lower power applications (eg
USB lamps, power banks, etc)

Theo