Date   : Wed, 24 Aug 1994 11:28:29
From   : JAMES WARD <J.Ward@...>
Subject: Re: Video display.

Someone said (ages ago...)

>I was wondering if 128 cycles/scanline is still true for non-
>standard graphics modes, such as the 256-byte per scanline one....

This is a factor of the UK television system which has a 15.625kHz
line rate, hence 64us (micro second) per display line.  Some of this
is active display time (about 40us I think), some is sync. pulses
(and colour burst etc.) and some is horizontal flyback (about 21us I
believe.
128 cycles corresponds to this 64us period, hence modes which break
this convention may not synchronise properly on UK televisions.
I also believe that the line rate of NTSC system is the same (it has
fewer display lines to squeeze in the extra frame rate, without
changing the line rate... so this is probably also true of NTSC
systems.
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( E-Mail:  j.ward@...                                        )
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