Re: IIgs video modes...

[Linards Ticmanis <ticmanis@gmx.de>]

Michael J. Mahon wrote:

>>> In the personal computing world of the early 1980s, there were two
>>> video "camps":  those who used the artifact color trick and those
>>> who didn't.  One glance at the master clock frequency was usually
>>> enough to tell the difference.  ;-)
>>
>> Hmmm... Commodores use a 14.31818 MHz main quartz too (the NTSC
>> versions, that is). Their pixel clock is quartz frequency divided by 7,
>> then multiplied by 4.
> 
> But did they also use the 14MHz clock divided by 4 for the chroma
> subcarrier frequency?  In that case, they just saved having to add
> a 3.58MHz crystal for the chroma modulator.  I suppose that saved
> a fraction of a dollar.

Yes, that's the case. And we all know how cheap they were... ;-)

Though deriving everything from a single quartz probably also cuts down
on Moir� effects, of the kind that plague the PAL Apples.

In fact they used 17.733475 MHz crystals in their PAL models and divided
that by 9 for the "1 MHz" CPU clock, ending up more than 4% slower than
the NTSC boxes.

-- 
Linards Ticmanis