CL1B power distribution

pgf at pgf at
Sat Apr 25 19:29:34 EDT 2009

wad wrote:
 > This is the current power distribution diagram for A-phase CL1B,  
 > identifying what we can power, when, and how.

wad -- 

a few questions -- for some i can guess at the answer, but better
to ask and be sure:

    - if there are no USB devices inserted, is there an advantage
	to powering down USB?  i.e., does it affect anything more
	than the devices themselves?

    - same question for SD?

    - the keyboard/touchpad are now optionally powered in suspend
	and run.  do you have a specific use case in mind?  the
	only case i can think of is turning them off if we're
	suspended and don't want their wakeups anyway.

    - will we have (approximate) numbers at some point for how
	much power any given subsystem takes?  (e.g., for the
	above case, how much would powering down the kbd/tpad
	save?  this will inform decisions like "how much effort
	is it worth?")

    - i can't believe i'm asking this, but is it feasible to only
	power half the ram?  would that help the power budget? 
	i have no idea how that feature would be put to use.
	or, perhaps more manageable:  half the flash?  if half
	were unmounted when not in use, for instance.

    - comparing with
	(which i'm assuming is "correct" for XO-1), i see the audio
	amp could be powered down before.  is that integral to the
	"HD Audio Codec" box now?

    - also comparing with that page, the RTC battery charger is
	always on now, and wasn't before.  from our conversation
	on IRC, it sounds like the circuit hasn't changed -- is that
	right?  (and that it's less a "charge" circuit than an
	"anti-discharge" circuit.)

 paul fox, pgf at

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