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 Post subject: Re: AVS for NES dev?
PostPosted: Sun Jan 22, 2017 12:53 pm 
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Joined: Sat Feb 12, 2005 9:43 pm
Posts: 10714
Location: Rio de Janeiro - Brazil
rainwarrior wrote:
Where were you told this? We speculated that it might not earlier in this thread but nobody posted a definitive answer / source about it.

Was it speculation? I could swear whoever said it was stating a fact. Sorry about that. I really don't want to propagate any misinformation.

 Post subject: Re: AVS for NES dev?
PostPosted: Sun Jan 22, 2017 2:04 pm 

Joined: Tue May 28, 2013 5:49 am
Posts: 999
Location: Sweden
I also compiled a list of compatibility considerations for various types of Famicom and NES systems. Here is an excerpt from a PAL perspective (Rainwarrior already mentioned some though):

Famicom only
* The oldest Famicoms (before the RP2A03E CPU) doesn't support looped noise. These Famicoms aren't that common though so I wouldn't care about this too much (besides looped noise is a cool sound).
* Only late Famicoms (RP2C02G-0 PPU and later) has a readable $2004 so it's best not to rely on its readability (Codemaster games tend to read it though). These Famicoms are common and includes earlier Twin Famicoms.
* $4016.1 and $4017.1 needs to be read, and if they are not used for 4 player mode, they needs to be merged with controller I and II data so that Famicom users can use external controllers with your game.
* Start and Select is missing on controller II so the game shouldn't require those buttons. If $4017.1 is merged with controller II though, it will be possible to press Start and Select via an external controller.
* If you want four player mode, you'd need to read $4016.0 as controller I, $4017.0 as controller II, $4016.1 as controller III and $4017.1 as controller IV. A Four Score can't normally be connected to a Famicom.

NTSC Systems (NTSC NES and Famicom)
* Red and green emphasis bits are reverse from PAL NES.
* Vertical blanking period is shorter, can't use the full PAL vblank time.
* Faster CPU clock (sprite movement speed, scroll speed and music tempo)
* APU Pitch is different
* Raster effects will need to be different from PAL

RGB PPU (Sharp C-1 and Famicom Titler)
* Grey colors $D2 and $D3 are missing so it's best not to use them ($00 and $10 are good greys to use)
* Color emphasis effects brightens the colors instead of dimming. Setting all three bits makes the screen totally white and the player can't see anything.

Dendy (and some other PAL Famiclones)
* Emphasis bits red and green are swapped in $2001 just like on PAL NES.
* UMC based CPU clones have swapped 25% and 50% Duty Cycles for the Square Channels.
* Speed is like PAL (affects sprite movement speed, scroll speed and music tempo)
* APU Pitch is like NTSC
* Raster effects will need to be like NTSC
* Some Famiclones are both missing Start/Select and the microphone on controller II so you don't want to require the player to do any of these inputs.

So Dendy is like a mix of PAL and NTSC. You might want the player to be able to mix and match speed and pitch settings however he wants in an options menu if you want to safely support NTSC, PAL and Dendy.

WheelInventor wrote:
I plan to get a PAL NES again (our old one was thrown in the garbage by my sister :cry: )


It belonged to her so she took it to her home one day when she was bored and wanted something to do. Years later I asked her what she did with it and it turned out that she had thrown it out because the games didn't work anymore. It wa probably just a cart connector problem...

But they are so darn expensive nowdays!

I got my second one (including box and everything) for ~600 sek off tradera. That was two years ago, though.

Right now there's two superficially dysfunctional units up...

Oh 600 kr is a good price for a CIB system.
Yeah thanks, I've been scanning Tradera and ebay now and then to get a feel for the current prices. The problematic cart connector in NES systems is one reason why I hesitates.

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