Re: VIC-II and luma levels

From: Segher Boessenkool <>
Date: Fri, 13 Jan 2012 18:38:10 +0100
Message-Id: <>
>> The LUM signal has an external pullup; everything inside the VIC-II
>> does pulldown only.
> Yes... And that pullup is integrated into the RF modulator. Which  
> makes removing the modulator to improve picture quality a pain.

It is outside of the modulator on the oldest boards.

>> The newer chips supposedly are nine levels, just like PAL; but  
>> indeed,
>> when did they change from five?
> I found this picture today while trying to do some further research:
> luminances.gif
> From this image is looks like they were still finetuning the  
> resitor values after R3. Too bad the image doesn't contain values  
> for the HMOS versions.
> And here's some other information:
> luminances.txt

Interesting stuff.  I remember that picture yes.

It's not clear to me if those measurements all use the same
external circuitry (like, modulator).  And there is quite some
variability between (batches of) chips, so you really need to
test a bunch of each revision to see if there is really a
difference :-(


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Received on 2012-01-13 18:00:24

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