#10512 NORM Future : XO-1, XO-1.5 and XO-1.75 A1 external SD card slot does not discharge supply (was: XO-1.5 and XO-1.75 A1 external SD card slot does not discharge supply)

[Zarro Boogs per Child]

#10512: XO-1, XO-1.5 and XO-1.75 A1 external SD card slot does not discharge supply
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           Reporter:  Quozl                |       Owner:  Quozl                                  
               Type:  defect               |      Status:  new                                    
           Priority:  normal               |   Milestone:  Future Release                         
          Component:  ofw - open firmware  |     Version:  1.5/1.0 Software Build os852 aka 10.1.2
         Resolution:                       |    Keywords:                                         
        Next_action:  code                 |    Verified:  0                                      
Deployment_affected:                       |   Blockedby:                                         
           Blocking:                       |  
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Comment(by Quozl):

 XO-1 schematics reviewed, it may also be affected, though to a different
 extent.  There is only 4.8uF of capacitance on VCC_SD compared to 15.7uF
 on XO-1.5.  The clock and data interfaces are entirely different.

 Tested three cards on XO-1 (q3a61c) and XO-1.5 (q2e45q -r2065), evaluating
 the time taken to display a directory, given various power off times.
 Graph of results at http://dev.laptop.org/~quozl/10512/ ... summary:

 ||''n''||''card''||''model''||
 ||95 ms||ADATA 4G microSD class 2||XO-1||
 ||60 ms||SanDisk 4G microSD class 2||XO-1||
 ||60 ms||SanDisk 8G microSD class 2||XO-1||
 ||160 ms||ADATA 4G microSD class 2||XO-1.5||
 ||45 ms||SanDisk 4G microSD class 2||XO-1.5||
 ||45 ms||SanDisk 8G microSD class 2||XO-1.5||

  * below time n, the card has not turned off or reset, and access is rapid
 (XO-1), or fails utterly (XO-1.5),
  * at time n, the card may require a repowering (the four second delay,
 XO-1), or fail utterly (XO-1.5 SanDisk),
  * beyond time n, the card has reset and requires an additional 500ms to
 start up,
  * n is lower for XO-1 than XO-1.5, presumably due to lower capacitance,
  * n correlates across the two SanDisk samples,
  * n is always below 200ms.

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Ticket URL: <http://dev.laptop.org/ticket/10512#comment:2>
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