Rockbox Development > New Ports
SanDisk Sansa c200v2, m200v4, clipv1, clipv2, clip+, and fuzev2
saratoga:
--- Quote from: bertrik on May 07, 2009, 10:34:22 AM ---If we run the processor at less than 200 MHz, the core voltage can be reduced from 1.2V to 1.1V, according to the as3525 datasheet (see the note in paragraph 6.2.2) . This could save some power (in a simple approximation dissipated power is inversely proportional to the *square* of the voltage). I think we don't really *need* to run at absolute maximum speed of 248 MHz, so we could save power by running slightly lower than 200 MHz.
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Can it be adjusted on the fly? If so, the beast has the same problem due to its frequency/voltage scaling. We should probably consider a more general solution to this problem, either by having more complicated boosting code or by allowing codecs/plugins to request a higher clockspeed/voltage level.
--- Quote ---By the way, I noticed that AMS has a new revision (rev1.13) of the as3525 datasheet on their website, see http://www.austriamicrosystems.com/eng/Products/Mobile-Entertainment/High-Performance-Microcontrollers
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" Added definition of Power Management Output Voltages"
kugel.:
--- Quote from: Llorean on May 07, 2009, 10:42:19 AM ---You really should make the full speed available while boosted, I'd imagine. Otherwise you're potentially cutting off file formats (ApeV2 at certain compression levels possibly) as well as restricting the bitrates and possibly resolutions at which video can be encoded.
The whole point of being boosted is that things that need a large amount of CPU can get the full capabilities of the player behind them.
If there's a role for "not quite full power" it should probably be engineered in as a general thing, rather than choosing to limit just one port (well, set of ports).
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That would probably also mean to to lose our zero-wait boosting. Sad thing, but I generally agree with you. However, zero wait boost is probably wanted once we get more into a gui boost.
FlynDice:
--- Quote from: bertrik on May 07, 2009, 10:34:22 AM ---If we run the processor at less than 200 MHz, the core voltage can be reduced from 1.2V to 1.1V, according to the as3525 datasheet (see the note in paragraph 6.2.2) . This could save some power (in a simple approximation dissipated power is inversely proportional to the *square* of the voltage). I think we don't really *need* to run at absolute maximum speed of 248 MHz, so we could save power by running slightly lower than 200 MHz
--- End quote ---
Can we adjust that voltage somehow or was that a choice sandisk made when they designed the player?
saratoga:
The AMS chip has its own voltage regulators which are under software control.
FlynDice:
Ah yes found it now.
Does this note on the next page under 6.2.3 have any bearing on this lower frequency?
(1) This setting must not be used for AS3525 core supply because the lower voltage limit is out of core supply specification limits.
EDIT: I suppose this could apply for the above 200Mhz clocking and if we're below that the note on the previous page would apply. Otherwise why would there be a setting for lower?
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