I'm curious about the transistor count of the VIC-II, the video chip in the Commodore 64. According to http://visual6502.org/wiki/index.php?title=Chips_in_our_collection the Atari 2600 TIA chip has 6193 transistors; each of the custom chips in the Amiga has about 20,000; I would intuitively expect the VIC-II to be somewhere in between those two.
It occurs to me that one possible line of reasoning is based on the existence of 'bad lines' when the video chip reserves more bandwidth to read character data (40 bytes) and color data (40 nibbles), or more specifically, the fact that these occur only once every eight scan lines. That means the data must be stored in the chip for the next seven scan lines, until the next row of characters.
40x8 + 40x4 = 480 bits. The usual count of transistors to store a bit is six transistors in a flip-flop, so that's 2880 transistors. There will also be access circuitry; let's round it up to 3000.
That wouldn't be very informative lower bound on the chip size, but it is also said that about 70% of the chip area is spent on sprites. That brings the lower bound (if sprites and character/color buffers were the only components) up to 10,000 transistors. In practice, there are also other components; the actual size might be something like 15,000 transistors?
Does anyone have a more accurate estimate? If not, does the above reasoning look sound and the above estimate look in the right ballpark?