Re: Why did Woz use the long cycle?

["Michael J. Mahon" <mjmahon@aol.com>]

On Apr 4, 5:21 am, ferd...@gmx.de wrote:
> In the Apple ][ the long cycle is used to maintain a constant
> relationship between COLOR REFERENCE and the horizontal scans. I'm
> just wondering why a constant phase relationship is needed. If there
> was no long cycle, the COLOR REFERENCE would toggle each line, as
> intended by the NTSC standard. Some modifications would be necessary
> though:
> The vertical counter needs to be synchronized to the alternating COLOR
> REFERENCE phase. I would feed COLOR REFERENCE to D13-6 (see
> Understanding the Apple ][ page 3-14), so that the counter latches the
> state of COLOR REFERENCE when preset instead of toggling before every
> preset.
> The H0 signal fed to A8-14 (page 8-12) needs to be XORed with VA.
> In HIRES mode programming needs to be changed to compensate for the
> alternating phase relations.
> I'd expect better picture quality because straight vertical lines
> would not be colored in one color but alternating green/red or blue/
> orange. If the TV has a comb filter, the lines would not be colored at
> all.
> I don't have an old apple ][, I just have //e's, so I can't try it on
> my own.
> Does anybody know other reasons for the long cycle?

The fact that it makes it possible to draw vertical lines of a single
(constant) color is a pretty good reason!

-michael