[Trac #1419] Screen refresh rate should be dynamic to save power.

[Zarro Boogs per Child]

#1419: Screen refresh rate should be dynamic to save power.
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 Reporter:  jg               |        Owner:  JordanCrouse
     Type:  enhancement      |       Status:  new         
 Priority:  normal           |    Milestone:  BTest-4     
Component:  x window system  |   Resolution:              
 Keywords:  power            |  
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Comment (by gnu):

 Unfortunately, slowing down refresh involves slowing the dot-clock rather
 than just inserting lots
 of time between the end of the last pixel, and the beginning of the first
 pixel of the next frame,
 the way old CRTs had a very long vertical retrace period to account for
 electron beam movement.  The slow dot-clock means that we are stuck with a
 longer-than-usual delay before we can get either changed pixels, or
 changed settings (CPU image versus DCON internal image) to the screen.

 Perhaps this can be re-examined in a Gen 1.5 or Gen 2 design.  Programming
 the CPU video for a high speed dot-clock but only a few frames per second,
 would probably allow the refresh rate to be rapidly ramped up at all
 times.  (If the CPU video is in vertical retrace when you ask it to
 change, it can just end the vertical retrace and start a new frame
 immediately.  If it's in mid-frame, it can switch to the new vertical
 retrace timing at the end of that frame, immediately scanning out the next
 frame.  I don't know if our current CPU video chips can change their
 vertical retrace timing on the fly without glitching.)

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Ticket URL: <http://dev.laptop.org/ticket/1419#comment:2>
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