[Coco] [coco] video signal generation
farna at att.net
farna at att.net
Fri Jan 5 22:55:45 EST 2007
Roy, one thing I do recall about the CoCo3 GIME chip -- it's SLOW!! It won't take anything over the 2MHz speed of the CoCo3. Anything over pushes it to much and you get garbage on the monitor. I know that's the main reason there have been no speed upgrades for the CoCo3 CPU -- the GIME uses the same clock. Speed up the CPU, destroy video output. A faster CoCo3 would need a terminal connectoed to it -- might be workable for OS-9, but not DECB. And in that case, an emulator running on a PC connected to a CoCo as a terminal might be the best solution.
I know, doesn't help your problem one bit! (sorry)
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> >On Thursday 04 January 2007 21:25, RJRTTY at aol.com wrote:
> >>I have been struggling with a problem with my converter for a while
> >>and I need some information.
> >>Does anybody know the details of how the GIME generates a
> >>RGB video signal? The problem I am having is that while 80 col
> >>text on the green channel is clear and sharp, 80 col text on the red
> >> shows some video degradation and 80 col text on the blue channel is
> >> completely illegible.
> >>What I am thinking is that the GIME generates the green channel first,
> >> the red channel second and the blue channel last. Is this correct?
> >> Another strange thing is that 80 col text in any color combination
> >> that has even a little green in it shows up well but if you look at
> >> 80 col. text using pure red or blue as the foreground or backround
> >> you get a wierd kind of video smearing.
> >>I already have a solution. If a low pass filter is placed in the
> >> input channels
> >>the 80 col text shows up well in all color combinations. In other
> >> words I had
> >>to DECREASE the bandwidth of the converter in order to get acceptable
> >>results. It seems that the quality of the video signal coming out of
> >> the GIME in the coco3 is only slightly better than the old monitors
> >> could display and the high bandwidth of my converter is just too much
> >> for the signal showing it "warts and all".
> >>I don't know about the rest of you but purposely degrading the
> >> converter to approximate the perfomance of the old monitors just
> >> seems wrong to me. The image does soften a tiny bit with the filters
> >> but not enough to notice if you were not already looking for it or
> >> directly comparing it to an unfiltered converter.
> >>Does anybody know what is going on with the conversion process in the
> >>GIME to cause this?
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