Re: Procep SECAM Re: C16/Plus4

That was a case of not bothering to implement a SECAM TIA at all. Instead 
the French 2600 used a PAL TIA and ignored the chrominance output 
completely. The three luminance bits were used to generate FM chrominance 
frequencies in addition to generating the luminance levels, hence only eight 
colours.

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From: "Anders Carlsson" <anders.carlsson@sfks.se>
Sent: Wednesday, November 02, 2011 1:25 PM
To: <cbm-hackers@musoftware.de>
Subject: Re: Procep SECAM Re: C16/Plus4

> Richard Atkinson wrote:
>
>> One of the luminance outputs of the GTIA had to be removed in order to 
>> free up pins for the VCO interface, so the SECAM Atari 800/XL/XE only has 
>> eight luminance levels (128 colours) rather than the sixteen (256 
>> colours) of the NTSC and PAL GTIAs.
>
> Although out of scope for cbm-hackers, does this in some way relate to the 
> SECAM version of the TIA used in the Atari 2600? While the NTSC and PAL 
> versions output a bit over 100 colours each (the exact numbers vary and I 
> can't be bothered to look them up), the SECAM Atari 2600 only outputs the 
> eight base colours black, white, red, green, blue, cyan, magenta, yellow. 
> I never tried to figure out /why/ that is, but your very detailed 
> explanation of SECAM and removed luminance on the GTIA sounds like 
> something similar but yet more extreme had to be done with the 2600.
>
> Best regards
>
> -- 
> Anders Carlsson
>
>
>
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