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Overclocked

Posted: Thu Jan 17, 2013 10:39 am
by Angel
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Hi all!

The uzebox Overclocked to 28.61818Mhz, would it be possible to increase the speed? How high? Could we extend the graphical resolution to this?

Thank you very much for the answers

Re: Overclocked

Posted: Thu Jan 17, 2013 3:51 pm
by Janka
Angel wrote:The uzebox Overclocked to 28.61818Mhz, would it be possible to increase the speed?
The clock rate has to be a integer multiple of exactly 3.579545 MHz, otherwise the NTSC color coding won't work (with RGB output, this restriction is nil).
So the current clock rate is 28.63636 MHz is 8 times that NTSC color burst frequency. The next integer multiples are at 32.215905 MHz and 35.79545 MHz, which is both nearly impossible to get a crystal for. So we'll had to use a PLL to synthezise these frequencies, which adds a lot of additional hardware and problems to the Uzebox.
How high? Could we extend the graphical resolution to this?
Uze has sure tested how high the overclocking works. I doubt it goes much higher than 35 MHz. The graphical resolution could be extended a little bit (e.g from 240 to 300 pixels in a row at 35.79545 MHz and mode 3).

Re: Overclocked

Posted: Thu Feb 07, 2013 3:48 pm
by tysonedriscoll
Janka wrote:The graphical resolution could be extended a little bit (e.g from 240 to 300 pixels in a row at 35.79545 MHz and mode 3).
Is it possible to extende graphical resolution more?

Re: Overclocked

Posted: Thu Feb 07, 2013 11:16 pm
by D3thAdd3r
tysonedriscoll wrote:Is it possible to extende graphical resolution more?
It's already 143% of the 20mhz max speed specification, and not every '644 chip can even do the uzebox rate of 28.636. Whatever small percent of over-volted chips could do 35, get 1-2 extra cycles a pixel and still only have 4k ram to work with...so it wouldn't be a super nintendo/famicom all of a sudden :|