i was thinking after reading the posts her about pushing the nes to its limits and about the "hellraiser" cart, and i had a strange idea. i would normally just describe my idea, but since i am sleep deprived and probably not making alot of sense at the moment, i made a nifty block diagram :)
what i am thinking, is using a microprocessor on the nes cart that uses the NES for input an output, but does the processing itself. then, have a basic library that programmers could use to make games for this cart, systems like screen bliting for multiple bg layers, transparency, etc. and basic nes input output. the only thing that i can think of that might be a problem , is finding a method to make sure the NES and the Cart dont both try to read or write to the expansion ram at the same time. this cart might be a little expensive, but if you do something like the Alladin deck enhancer that has a smaller cart connect to the main cart, it could be done in a cost effective way so that people could buy one cart with the microprocessor, and then as many "mini" game carts as they wanted (or as there are out).
1. load the boot code to control the security bypass circuit to disable the lock chip.
2. write $00 to $ff to NAM table, repeating every 8 rows
3. enable NMI routine
1. write to certain byte of expansion ram to tell the microprocessor on the cart that vblank has happened (so we can help keep it in sync with the ppu to calculate where it is refreshing
2. grab joypad and other information write to expansion ram on cartridge
3. read information from expansion ram that the microprocessor has put there for the PRG rom to write to certain registers inside the NES (such as music?)
1. run the game rom (could possibly be programmed in c/c++ so someone doesnt have to know/understand 6502 assemble, and so more people could program thier favorite 8 bit beast)
2. renders information in a screen buffer to CHR RAM, changing the patterns every 8 rows to get pixel X pixel control
3. maybe have the microprocessor cause an interrupt on hblank to have fun with the palette?
well, that is my basic idea, i have not thought much about the major technical issues that would be involved, but i bet someone could find a way to make it work, rite? and with any luck, someone would use this power to make a good ol' fashioned powerfull nes type game and not one of the new style 3d ones where you dont do anything special except run around :P