Re: 6561 (PAL VIC-I) interlace mode bit

From: Segher Boessenkool <>
Date: Sun, 28 Aug 2011 00:31:26 +0200
Message-Id: <>
>>>> I've looked at the Y decoder on the 6561 (PAL) chip.
>>> Sorry if I didn't follow the discussion, but what does "look" mean?
>> Look at this:
>> (I don't make the pictures, I just look at them, fwiw).
> Still, looking at a die shot and being able to find out what the  
> structures mean is not an easy thing... Is there a die shot of a  
> VIC that tells you what the different parts are?

There is this one:

It's not completely correct, and it leaves out all of the fun details.
Much too small for more details of course, but maybe it gives you an

When figuring out a chip, I usually start with the address and data
busses, from there the internal registers, and then the various clocks
(there are 12 clock signals on the VIC-II! -- 1, 2, 4, 8MHz, each two
phases, and colour clock, four phases).  It's depletion load NMOS, which
is quite easy to read once you get used to it (and have good  
pictures :-) );
but almost every chip gives you some new structures (to keep it  
e.g. the VIC-II has bootstrapped clock gates (lots of them) and of  
the various analog stuff.


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Received on 2011-08-27 23:00:27

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