Re: [stella] playfield on-the-fly updates

["José Carlos" <zezao@xxxxxxxxxxxxxxxxx>]

Please, do not send me more msg!!!

Chris Wilkson wrote:

> At 11:34 18.05.98 -0700, you wrote:
> >Sounds like you have 2 clock cystals.  Could one be for SECAM? It's
> >interesting to note that 3.54 is 80% of 4.43.  Sounds like it's a dual
> >standard machine.  NTSC runs at 3.5795MHz.  Actually, if you use the the
> >3.54MHz crystal, that's "close enough" to NTSC.  And if you use the 4.43MHz
> >cystal, you can get 324 scanlines at 60Hz, or 388 scanlines at 50Hz.
> >Sounds kinda "convenient" to me.  If anyone here has an extra PAL 2600 jr,
> >and could send it to the states, I'd really like to disect one.
>
> I don't think, that the second clock is for SECAM. SECAM uses
> a completely diffent colour encoding scheme, so there wouldn't
> be much use of a dual standard version, if you still have to
> change parts. Also there would have to be a possibility to
> set the standard to use, right? But the only thing adjustable
> are these two screwlike parts, which I think are for something
> else. There are two chrystals in my 6-switch model too, but
> they are labeled with generic Atari part numbers, which don't
> say anything about their speed.

I think it was probably to enable both NTSC and PAL to run at the same
framrate.  But I don't know.  You're right about the need to switch
standards.  I don't know how it would have been done, though.  The two
screwlike parts I can identify for you.  The flat, really cheap looking
thing is a pot (variable resistor) for adjusting the color burst delay.
It allows you to shift the color set "to the left or right" within the
spectrum.  The more expensive looking, probably tall and enclosed in
plastic thing is a variable inductor.  This fine tunes the RF output
frequency.  *NEVER* touch this one!!  It's nearly impossible to get it
back to the factory setting. :O

> BTW, if you pay for the shipping, you can have one of my
> PAL 2600 jrs. for free. I don't know the exact prices, but
> I think surface mail would be about $10 and airmail about
> $17. Or you could trade it for a finished megacart and pay
> no shipping. :-)

Cool!  Email me your address and the shipping to California, and I'll
mail it out.  Thanks!  Sorry, but mailing you a Megacart now would be
like giving you a puppy that has no fur... :)

-Chris
 

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