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1 user currently in Rom Hacking:  hukka |
| Acmlm's Board - I2 Archive - Rom Hacking - How do you port FDS games to .nes files? |
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NMorgan Micro-Goomba Level: 7  Posts: 16/16 EXP: 1406 For next: 42 Since: 07-07-04 From: New Jersey, USA Since last post: 78 days Last activity: 75 days |
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| I know SMB2(J) has been ported to a .nes file, because the author of NESticle did it. But there is another FDS game I want to port to a .nes file, so that I can transfer it onto a cartridge and play it on my NES. The game I want to do this with is called Ai Senshi Nicol, which is one of the greatest games you've never played. So basically: what must be done to port a .fds ROM to a .nes ROM? I have moderate ROM hacking knowledge, I'm really not that great, but I'm not completely ignorant. I'm sure some degree of ROM hacking will be required to do this. Any help is highly appreciated. Thanks in advance. |
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Dish Spiny Level: 38 Posts: 529/596 EXP: 355646 For next: 14801 Since: 03-15-04 From: Disch Since last post: 18 days Last activity: 18 days |
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| It's very similar to a mapper change -- only you have a lot of free space since what was previously used as FDS BIOS can be used for initiation code and other goodies (excluding the areas of BIOS the game actually uses). However it comes with several problems: 1) FDS disk images are (as the name suggests) floppy disk images -- they are not ROMs. Floppy disks are a form or RAM, not ROM. So FDS games can write to what's normally ROM space and it will actually change the data there (behavior which does not exist on the NES). If you are going to move this to NES, you will have to find all the areas in the game which write to PRG-RAM and find a way around it. It might be as simple as changing the space to somewhere free in cartridge SRAM -- or it might be difficult if, say, the game has self-modifying code. 2) FDS has a scanline IRQ counter. If the game uses it, you'll have to pick a mapper which also has a scanline counter -- this may involve heavy code rewrites unless the IRQ counters work very similarly. 3) FDS has an extra sound channel which obviously won't play on an NES. And yes, Ai Senshi Nicol uses this channel. Quite heavily in fact. If you're going to play it on an NES, prepare yourself for some very dull sound. 4) I *think* FDS can put PRG-RAM at $6000-7FFF. The only NES mapper I know of which does this is FME-07 (it can put either cartridge WRAM or PRG-ROM at $6000-7FFF)... and good luck finding a compatible FME-07 board -- your best bet would be Batman: Return of the Joker -- but I'm not even sure if that has the PRG@6000 capabilties (the game doesn't use it). You might need to get a copy of Gimmick! (or the PAL version Mr. Gimmick). I don't know really if FDS can do this though -- I haven't looked into FDS all that much. And even if it does this will only be an issue if Ai Senshi Nicol puts PRG there -- odds are it keeps RAM there, in which case it's not a problem. 5) If the game uses any info from the FDS BIOS you will have to put the routines it uses in the ROM. 6) There are probably other potential complications, but these are all I could think of off the top of my head All of these issues probably won't be a problem -- but some of them will. Basically it comes down to three things: - Knowing the details about the NES - Knowing the details about the FDS - Knowing the details on the target mapper you want to switch to If you can do a proper mapper change hack -- like say take a MMC1 ROM like Kid Icarus and convert it to use MMC3 -- then you have the idea of what more or less needs to be done for an FDS conversion. If MMC1->MMC3 is too tough -- then you probably won't be able to change from FDS->xxxx ... it's far more difficult. EDIT Having actually looked at the game in question a little bit, it might not be all that tough. Doesn't look like the game uses the IRQ counter -- but it does fill $6000-7000 with something -- but it looks like RAM (BIOS moving it there? perhaps FDS doesn't really swap in PRG??) The game seems simple enough -- for some reason I was expecting it to be more complex. So yeah... the biggest problem looks like the sound... which unfortunately you can't do anything about. Nothing else looks like it'll be a problem though. At least not at first glance. I say get yourself some FDS docs and start futzing around ;D I don't have any to recommend unfortunately, but I'm sure there are plenty on nesdev. (edited by Disch on 08-16-05 01:44 AM) |
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KawaiiImoto-e Hammer Brother Level: 49 Posts: 958/1068 EXP: 852917 For next: 30966 Since: 03-15-04 From: In my own little complicated dreamworld Since last post: 16 days Last activity: 4 days |
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| Disch put it nicely what would have to be done. and about the SMB2(j) NES-ROM, its just a pirate cart patched to work with NESticle. Your attemt is interessting and a real challenge to put of. But if you want to make a cart, it may come cheaper to just hunt down a Famicom Disk System on ebay.co.uk and the game. (There is a Honk Kong based seller wich can't sell his famicoms anymore in Hong Kong) |
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Mega-Dog Level: 20  Posts: 82/139 EXP: 40051 For next: 2388 Since: 03-15-04 From: Minnesota Since last post: 8 days Last activity: 4 days |
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| A long time ago there was an utility I saw to convert them, but this musta been almost 4-5 years ago... |
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