Re: C65 on Ebay

Hi!,


On 2017-11-04 16:56, smf wrote:

> I'm not entirely convinced that even composite video comes under NTSC or
> PAL, which were originally RF broadcast video standards.

NTSC might have started as a monochrome baseband video encoding schema,
yet, it was not a terrestrial broadcast (RF) standard. For most of NTSC
areas, CCIR System M described the details of how the baseband video
signal was supposed to be modulated for terrestrial transmission over
RF. PAL (Phase Alternating Lines) as the name implies never denoted even
a black and white baseband video encoding schema.

> The c64 doesn't
> output legal NTSC or PAL in any case, which causes problems for some
> modern TV's.

AFAIK, not even the Amiga is fully correct in this respect... it still
produces scanlines of integer multiple lengths of the (respective)
standard color subcarrier cycle. Strictly speaking, this is still a
violation of the standard (or, "just works", if you please - a better
approximation, but not fundamentally different from the rest).

>> The 64 has to be either PAL or NTSC due to the fact that the integral, internal hardware encodes colour into chroma line and one can't put his fingers on any other form of the signal.
> 
> If there was a cost advantage to including both PAL and NTSC chroma in
> one package, then commodore could have done so.
> 
> Amiga's are either PAL or NTSC too, some have composite video output
> which is one or the other. The others still have different system clocks
> which match the video standard. You can't take an "NTSC" amiga and make
> it display a valid PAL signal, without modifying the hardware so that
> it's a "PAL" amiga.

To be truly dual standard, they'd have to have added an additional
oscillator plus some logic that'd choose the correct clock for the
current video mode. Probably this is what they were unwilling to do.
(They could have as well used a PLL frequency synthesizer, at the time
probably an even more expensive option than using a pair of
oscillators.) Let alone the additional details needed to have the late
budget models (600 and 1200) produce at least baseband PAL and NTSC
composite. (Proper B/G/M/J RF would have been yet another story).



Levente

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