I found a die photo of the NES video chip: http://visual6502.org/images/RP2C02/NES_RP2C02_G_8F1_1B_20x_1600w.jpg
I think the big block of fairly regular circuitry at the bottom left is the sprites? There is an 8x8-ness about it, and the NES has 8 sprites per scan line.
The big block of even more regular circuitry at the top right looks like RAM. What did the PPU store, that would take up that much space?
The irregular circuitry at the top left, I'm guessing implements tiles, the other major feature of the PPU.
Anyone have any idea what the semi-regular circuitry at the bottom right might be?
Though it's hard to be sure about scale, the whole chip kind of looks smaller (in terms of eyeball guess at transistor count) than the VIC-II. As I understand it, the VIC-II came out a year earlier, implemented in 5-micron CMOS, was a big complex chip for its time (best guess maybe 15k transistors), had initial yield problems. Maybe Nintendo went for a smaller chip because they didn't feel they could have an interim period of charging $595 for the machine the way Commodore did? Having only one mode would also help some.
But the thing I am most curious about is how small the sprite circuitry is compared to the VIC-II. Granted the sprites are smaller, but still 8 pixels 3 colors = 2 bytes, compared to 12 pixels 3 colors = 3 bytes, so I would've expected maybe 2/3 the size, but it's actually about 1/4 of the chip compared to 3/4, so that's more like 1/3 the relative size, and that of a chip that looks smaller. How?