Simply updating the color/pixels for the sprites is doable, but changing the size of the sprites so that they don't produce flicker (on the PCE), is a much harder task. This is what I was doing with Megaman. It's not just simply putting in a new size, but most NES 'sprites' are made up of smaller 8x8 sprites. If you substitute, say a 32x32 sprite (to remove flicker), for as a group of 8x8 sprites (a metasprite) - you now have to adjust for the 'offset' of that metasprite. That means building a new table and such to translate this all in realtime.
It's not processor intensive at all (quite the opposite since the processor is prepping less '8x8' sprites), but it's very tedious work creating these table values and testing them in game. Then there's the issue of clipping; NES only has 8bit screen coords and removes 8x8 cells from a sprite as they disappear on the edges (sometimes not so great either. You see popping on the edges of the screen, or wrapping). The game logic doesn't now how to deal with X and Y coords that are larger than 8bit (on the PCE they are 10bit), so you have replace this part of the original game's routine with your own. Otherwise whole parts of a sprite will disappear at the edge of the screen. Every game is different, so it's not like you can simply reused this replacement code as is for any NES2PCE game. It's game specific. All of this is.
So upgrading colors, music, and sound FX is pretty doable. Slowdown itself is usually automatically eliminated. But fixing flicker, by upgrading the sprite sizes, is no easy task.
The time it takes to get NES games, mentioned here in the past few pages, to run on the PCE wouldn't be much time in comparison to the time it takes to actually hack these games for upgrades. Upgrades means figuring out how a game works, nes2pce process to get the original rom running on the PCE does not require this; I only address how the NES hardware is supposed to respond to the game code - nothing else. And that usually means adjusting some timing or such (the large percentage of the emulation code is reusable across games).
But do you guys really want to play unmodified NES games on your PCE, though? I mean besides the cool novelty factor, which wears off quickly, what's the appeal if they aren't upgraded?
At some point, Megaman upgrade will get finished. My god, I've hacked that game more than I've ever hacked/replaced code in any retro console game. But I still have a ways to go. I still have Dragon Warrior to be released. And I still want to do a quick upgrade version of that as well (that game is actually partially hacked already for graphics). But please, don't hold your breathe on any of these. If you really want a specific NES game on PCE, I highly encourage you to get other hackers involved. I just don't have the free time to do this. But I do have the time to help explain things and even probably look into some problems.
To be honest, these are the plans that I had for nes2pce: Upgrade Arkista's Ring for 2-4 player TAP mode with enhanced graphics and music, upgrade Jackal with enhanced graphics, music, and 2 player mode, and upgrade Dragon Warrior with enhanced graphics and music. And upgrade Megaman 1 with graphics, music, and gameplay changes (6 button support, slide, etc). And possibly SMB with upgraded graphics and music. When any of these will be done, is directly related to the amount of free time I have. Man, I've wasted soo much of it over the years, too..
PS: Hey, did you guys know that "MottZilla" actually got NES Contra up and running with an old version of my nes2pce lib before I attempted it myself? He's an emulation author, but IIRC he dabbles in homebrew and hacking as well. Maybe someone should contact him and see if he's interested in a particular game for nes2pce? He's got the skills.
Edit: Also, if you want to know which NES games would probably be easiest to getting running on the current lib - look for NES games that use chr-ram (not chr-rom). There's a document out there called "nesmapper.txt" which lists a lot of NES game, and which ones use chr-ram (it's listed as "0k CHR"). CHR-ROM is doable, but I only had simple mapper support for it. And it's not refined. So the ones that list "0k CHR" are the best candidates. Of course, "8k CHR" games also work as well (no mapper for vrom).
