Re: DPMS state transition times

On Tue, May 13, 2003 at 05:43:59PM -0400, Manish Prasad wrote:
> Hi
> 
> I apologize if this isn't too relevant to this list.
> 
> I am trying to measure the time it takes to transition between DPMS ON
> state to various low power (standby, suspend and off) states, and back by
> instrumenting X server.
> 
> The X server, basically writes into hardware registers which ultimately
> turn off the screen and also turn off vertical and/or horizontal sync.
> 
> Is it possible to measure purely by software (say by polling a register)
> the time it takes for this transition to complete i.e. the time it
> takes to turn the display off after writing to the DPMS mode register.
> 
> I'm working with Intel i810 graphics hardware.
> 

You may want start to look if by chance the spec for the i810 already
have the answer, or if you want to stick with X, to ask XFree people.
But it should be better to look if the i810 fb implement DPMS.
IMHO, Linux is not RT, therefore, you can not be sure if X will
give you accurate results, but if you look for the frame buffer, you
should have better result.
You can then stick some rdtsc() and printk() in order to measure.

Cheers,

-- 
Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.


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