[Coco] 384 or 450 scanlines ?

Arthur Flexser flexser at fiu.edu
Mon Jan 13 13:59:45 EST 2014


I guess what's puzzling me is this:  as I now understand it, every
frame is ordinarily repeated twice in succession identically, with the
second repetition landing smack on top of the first, with a frame
occurring every 60th of a second and using only every other scan line.
 Wouldn't it have looked better if the second repetition was one scan
line offset from the first instead of on top of it?  Would the 6947Y
VDG accomplish that?

Art

On Mon, Jan 13, 2014 at 1:48 PM, Nick Marentes <nickma at optusnet.com.au> wrote:
> Arthur Flexser <flexser at ...> writes:
>
>>
>> Thanks for the explanation, John.  I'm curious, though, about why the
>> 6847 non-interlaced VDG was chosen for the CoCo rather than the 6847Y
>> interlaced version.  And, would a 6847Y VDG work if you replaced the
>> 6847 in a CoCo with it?
>
>
> And I thought that the interlacing was fixed in the TV/monitor of an
> interlaced set. That a monitor always provides 525 lines interlaced (NTSC).
>
> That's why I thought the CoCo had to provide either 2 fields or 1 field and
> a blank field to satisfy the interlaced function of the monitor.
>
> I guess it makes sense that the early video game systems and TV's would just
> create a single 262 line display that is repeated. I didn't know that the
> TV/monitor could stop creating the interlaced field.
>
> Nick
>
>
>
>
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