Re: Difference in luma-chroma delay of C64/C128 compared to standard S-video

From: Gerrit Heitsch <>
Date: Wed, 6 Sep 2017 15:21:20 +0200
Message-ID: <>
On 09/06/2017 02:33 PM, Mia Magnusson wrote:
> Den Mon, 4 Sep 2017 19:19:55 +0200 skrev Gerrit Heitsch
>> I remember the reason was to eliminate dot crawl. And since they
>> needed this disrecte PLL with the 74LS629 and the MC4044P for a
>> while, it can't have been cost reduction. And I also remember one
>> engineer saying that he now considers running the VIC with 2
>> different clock signals a mistake. They fixed it in the 264 series,
>> there TED gets the 14.318 or 17.734 MHz and does the rest internally.
>> The Amiga also runs everything from a single clock source.
> I'm not sure about the NTSC video output of A1000, and not sure about
> the built in stuff in A600 and A1200, but every other Amiga doesen't
> have any color clock at all as it only outputs RGB (and in some cases
> luminance+sync on a RCA jack).

Not quite true... All NTSC Amigas use a crystal with 28.636 MHz which is 
the NTSC color clock multiplied by 8. So there is color clock used, just 
not to encode the output signal. :)

PAL Amigas use 28.375 MHz, which is about 6.4 times the PAL color clock.

But in the text above I was only talking about the C64 and why they used 
this rather complex discrete PLL to derive the system clock from the 
color clock.


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Received on 2017-09-06 14:03:02

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