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PostPosted: Tue Apr 18, 2017 7:56 pm 
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Wasn't there also some talk about Hello Kitty World on the Famicom being, at least in part, automatically converted from Balloon Kid on the Game Boy, due to the strangeness of the 6502 in that game?


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PostPosted: Wed Apr 19, 2017 3:28 pm 
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Well, it's pretty funny. :roll: If you intend to convert a NES game to C, then to a x86 executable, it's no doubt you must emulate the hardware, otherwise you're blindfolded. An "engine" is an emulator. The C source code isn't true code, but something within blocks of data to replicate the PPU mechanics (bankswitching, tables, maps and scrolling).

Rockman Complete Works (PS1) has the original ROM on it, but when you run the game, there are a couple of differences - mostly, the lack of slowdown and no sprite flickering (8 sprites limit). Probably it uses an early prototype of such "engine", but still requiring the original ROM. At anyway, it's interesting. 8-)

Do you know if the NES Mini Classic use such engine, or all those games are, in fact, emulated?


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PostPosted: Wed Apr 19, 2017 3:52 pm 
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tokumaru wrote:
Wasn't there also some talk about Hello Kitty World on the Famicom being, at least in part, automatically converted from Balloon Kid on the Game Boy, due to the strangeness of the 6502 in that game?

The way that some of the tiny game logic quirks carry over perfectly hints at something like this.
I feel this way about Pac-Man for Neo-Geo Pocket Color. It is the only home port that isn't emulated that follows the AI so well and has the little quirks (like turning pac-man as he stops).


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PostPosted: Wed Apr 19, 2017 5:23 pm 
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tokumaru wrote:
Wasn't there also some talk about Hello Kitty World on the Famicom being, at least in part, automatically converted from Balloon Kid on the Game Boy, due to the strangeness of the 6502 in that game?

Yes, in this thread among others: viewtopic.php?p=24994#p24994

ccovell wrote:
On a related note, Hello Kitty World on the Famicom is a conversion of Balloon Fight GB on the Gameboy, and if it's not a totally automated conversion, it's at least pretty close IMO.

Making hacks for HKW was pretty tough, because for almost every variable in the game, the code does this:

load A with the variable from whatever RAM location
save it to $20-$2x in ZP
modify it in ZP
load it into A then save it back to whatever RAM location.

That always struck me as very Z-80-like.

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PostPosted: Thu Apr 20, 2017 6:53 am 
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Zepper wrote:
Rockman Complete Works (PS1) has the original ROM on it, but when you run the game, there are a couple of differences - mostly, the lack of slowdown and no sprite flickering (8 sprites limit). Probably it uses an early prototype of such "engine", but still requiring the original ROM. At anyway, it's interesting. 8-)

It's probably easier to just stick the entire program rom in there instead of just extracting the bits that you need to read as data. the CHR rom is a given, of course.

Quote:
Do you know if the NES Mini Classic use such engine, or all those games are, in fact, emulated?

Emulated, since people have been able to hack it to play any game in the NES library.


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PostPosted: Thu Apr 20, 2017 7:38 am 
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tepples wrote:
Dwedit wrote:
Companies are scared of using a real emulator for some reason, and want a port instead so they can avoid legal risks.

That and for a period of several months years ago, Apple's App Store Review Guidelines required a port because Apple was trying to kill Adobe AIR. Apple wouldn't sign an app for distribution to the public for use on iOS devices unless its source code (that is, the preferred form for making modifications to the program) was in either Objective-C++ or JavaScript.

I found a citation for Apple's former restriction on interpreters: Apple Eases Up on Restrictions on Interpreted Code in iPhone Developer Agreement, via Slashdot


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PostPosted: Fri Apr 21, 2017 1:59 am 
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Sumez wrote:
Quote:
Do you know if the NES Mini Classic use such engine, or all those games are, in fact, emulated?

Emulated, since people have been able to hack it to play any game in the NES library.

…though the emulator only had limited mapper support.


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PostPosted: Fri Apr 21, 2017 11:30 am 
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Mappers 0, 1, 2, 3, 4, 5, 7, 9 is still quite a lot of games. (yes, it even supported MMC5...) And if that isn't enough, you throw Retroarch on the thing.

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PostPosted: Fri Apr 21, 2017 5:48 pm 
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The only good game is DuckTales. Chip'n Dale wasn't fun, and I mean when I was 15 old. ^_^;; Talespin is the same.
Darkwing Duck... I got it as an hack (Mega Man 5) - you play as Mega Man. Later, I played the original game at all.


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PostPosted: Fri Apr 21, 2017 5:54 pm 
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I love the Chip 'n Dale and Darkwing Duck NES games!


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PostPosted: Fri Apr 21, 2017 6:04 pm 
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Zepper wrote:
I got it as an hack (Mega Man 5)

I remember that Megaman with a identity crisis!!
At least on the pirate hack I played at the begining of the stages and in the intoduction he screamed "I'm Darkwing Duck!"
I laughed out loud back in the day!! :lol:

tokumaru wrote:
I love the Chip 'n Dale

I liked Chip n' Dale too. Not that much, but was enough to make me finish the game.
I remember the last stage seemed atrocious to me back them.
I think I was 12 when I finished it... not sure though.

I need to revisit both them!!


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PostPosted: Fri Apr 21, 2017 11:25 pm 
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Dwedit wrote:
Mappers 0, 1, 2, 3, 4, 5, 7, 9 is still quite a lot of games. (yes, it even supported MMC5...) And if that isn't enough, you throw Retroarch on the thing.
2039 by Bootgod's count. (9's a singleton, though.)
My philosophy BG trained me to attack easily-refutable statements such as "all" or "not any"…

I recall hearing rumor that DWD uses a slightly-modded Megaman 5 engine. (The arrow probably led to this.)


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PostPosted: Fri Apr 21, 2017 11:41 pm 
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FYI http://decompiler.org/

ZSNES had the "Q" key to rewind very early from memory.


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PostPosted: Sat Apr 22, 2017 5:45 am 
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Oziphantom wrote:
FYI http://decompiler.org/

ZSNES had the "Q" key to rewind very early from memory.


Funny... this program expires 23rd June 2016. We have a problem! :mrgreen: :mrgreen:


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PostPosted: Sun Apr 23, 2017 7:33 am 
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Well... back to the topic. What kind of operations would replace "the skinny on NES scrolling" logic? Plus, what about cycle counting present in APU and PPU? Do you believe in code suppression like the NES scrolling and PPU reads/writes at all? Graphics are converted into a suitable format, ok, much like new memory for the NES RAMs (main, sprites and pattern tables), but I wonder about the inner PPU operations to get the game working fine.

If you take a timeline, we have the Rockman Complete Works on Playstation 1 using an engine that improves the original game code (no slowdowns, for example), but the ROM is still there (graphics were ported though). Later, the Virtual Console bringing copies of the ROM images built-in with an emulator + save states (remember the iNES header issue?). Then, Mega Man 9 and 10 - I wonder if this is the starting point for an engine and C port of the NES games. At last, the MegaMan Collection and Disney AC bringing such engine - games were ported to C and compiled.


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