Re: How does NTSC VIC-II produce 65 cycles per line

From: Bill Degnan <billdegnan_at_gmail.com>
Date: Thu, 12 Jan 2023 10:48:19 -0500
Message-ID: <CABGJBucmUi2LOcOqO3m+XdV1rZq9LDZ9cGWnja6DCs7C+fZVRQ_at_mail.gmail.com>
On Thu, Jan 12, 2023 at 10:15 AM smf <smf_at_null.net> wrote:

> I can envisage a few more issues than loss of color if using the wrong
> oscillator.
>
> IIRC the NTSC & PAL VIC2 use a different divider to generate the CPU
> clock, as they use wildly different oscillators.
>
> On 12/01/2023 14:54, silverdr_at_srebrnysen.com wrote:
>
> > The crystal change is needed because the frequencies (like chroma
> subcarrier) used by PAL and NTSC differ. Those are not synthesised but
> derived from the crystal frequency. Generally you can change only VIC chip
> and leave crystal in place and you'll still have output but there'll be no
> colour.
> >
>
>
I converted a P500 and a C116 to NTSC and if one does not chance the
crystal the color output goes "greyscale"
Here is a semi-technical writeup I did
https://vintagecomputer.net/browse_thread.cfm?id=258 in 2009

Here is the writeup I posted for the C116 conversion (PAL-->NTSC)
https://vintagecomputer.net/browse_thread.cfm?id=528

Bill
Received on 2023-01-12 17:00:43

Archive generated by hypermail 2.3.0.