[Coco] 384 or 450 scanlines ?

[Mathieu Bouchard]

Le 2014-01-09 à 15:37:00, Theodore (Alex) Evans a écrit :

> CGA uses the same scan rates as NTSC.  As the TV folks should confirm, 
> an NTSC field consists of 262.5 lines at 15.75kHz.  The CoCo does not 
> actually confirm to the standard as each field has a whole number of 
> lines making interlacing by just switching images every field not really 
> work right.  Some older 1024x768 VGA monitors and cards used interlaced 
> video, but basic VGA (640x480) is non-interlaced and all modern SVGA 
> displays are non-interlaced.

Sorry, I have not been sufficiently precise. VGA includes CGA modes (and 
same-resolution modes with more colours). VGA displays 200-line modes 
using 400 lines (not 480). However, I don't know why I wrote that it's 
interlaced, because it's not : VGA displays 60 full 320x200 frames (as 
60*400 lines).

I definitely didn't mean another meaning of the initials "VGA", which is 
the name of an image size used in video-projector jargon : 
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Vector_Video_Standards4.svg/960px-Vector_Video_Standards4.svg.png

And compared to EGA, VGA didn't only introduce 480-line modes, it also 
introduced 400-line and 240-line modes. The standard text mode that every 
VGA/SVGA PC boots in has 400 lines (25 rows * 16 pixels). There's not only 
one standard basic VGA picture size.

768 lines is definitely not VGA, it's made by what is called a SuperVGA 
card, though the projector jargon calls it differently, and though the 
plug is still called just VGA (because pin-compatible).

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| Mathieu BOUCHARD ----- téléphone : +1.514.383.3801 ----- Montréal, QC