[Open-graphics] video controller output clock

[Michael Meeuwisse]

On 4 Mar 2008, at 15:59, Timothy Normand Miller wrote:
>
> Exactly.  Howard's the one who knows what to do here, but he's a
> strapped resource, and there's tons the rest of us can do in the mean
> time.

Ok. I just encountered it while trying to figure out how the video  
controller was fitting together.

>>  I guess we could do something like, run at 130 MHz. Then we get
>>  640x480 - divide by 5.2 (count to 5, every fifth time count to 6?)
>>  800x600 - divide by 3.25 (count to 3, every fourth time count to 4?)
>>  1024x768 - divide by 2
>
> That's interesting, but it wouldn't leave you with a 50/50 duty cycle.
>  This could be a problem for the DVI transmitters, which are DDR.

I bet the screen doesn't like it either that pixels aren't coming in  
at a constant rate, which is what I meant  with 'odd'. I just don't  
know how else to do division and get somewhat accurate new clocks.

>>  Correcting the clock like that all the time is bound to give odd
>>  display results. So I don't know how to do it, but a divider sounds
>>  imho impossible.
>
> I'm going to get in touch with Howard and find out how he got it to  
> work.

Ok, great. :)

Cheers,

Michael
www.projectvga.org