Probably yes, the NES is "easier" in this regard since char-rom is read from cart (so a cart only needs to provide the bits in correct order), the GB(C)'s have video-ram that contains all parts so you need to transfer it over. Don't exactly remember but iirc classic GB was a tad too slow for this, but GBC has a DMA that might be fast enough. (I've developed on classic GB mostly so don't know the characteristics of GBC mode).
replyI played a bit with original gameboy too. I was very surprised when, iirc, the cpu is not even fast enough to clear the screen in one vertical blank, or even in one frame! It takes like three to fully clear the map.
reply