This might interest some of you.
http://www.ic2ic.com/search.jsp?sSearch ... 0&prefix=H
http://archaicpixels.com/index.php/HuC6260
It generates RGB and NTSC signals, has a 9bit pixel bus, 9bit data bus, 3bit red/green/blue for a total color count of 512colors, and a 512 color palette slot the 9bit pixel bus references. It asserts hsync and vsync triggers to whatever ic/processor that's driving the 9bit pixel bus. It also has 3 resolution available: 5.37mhz, 7.16mhz, and 10.4mhz dot clock (divided from a master clock 21.477mhz).
The common method for using the 9bit pixel bus is to have one layer (like sprites) uses the upper 256 color slots and background use the lower 256 colors. The chip commonly paired with the 6260 was the 6270 and used 4bit pixel format for 8x8 tiles with 16 sub palette and the same for sprites. The 0-15 sub palette was used as the top 4bits and the actual pixel data was the lower 4bits, of the 8bits on the pixel bus. The highest bit was set when sprite data was read out (same format 4bit palette/4bit pixel data).
The only problem is finding a setup that can feed the pixel bus at that fast a rate.
Also, The HuC6261 is a more advanced version with more color options.