Question about green tint on Dendy region

Discuss emulation of the Nintendo Entertainment System and Famicom.

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Individualised
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Question about green tint on Dendy region

Post by Individualised »

Sorry if this is a bit off-topic for this sub-forum but I think it's relevant enough.

How come that most emulators seem to swap the colour emphasis/tint bits for Dendy region, as they do with PAL region? I know that certain hybrid region UMC chip variants do this, but as I understand it this is not the case for the most common hybrid region clone chips. Since the hybrid/Dendy region is supposed to give NTSC programs maximum compatibility on 50hz timings, and that only certain chip variants swap the emphasis bits like PAL, it doesn't seem to make sense that most emulators do this.

In fact, I know of at least 2 games that were designed for a hybrid region chip without the colour tint bits swapped: Super Game's conversions of The Lion King and Aladdin. We can tell that they were developed with the hybrid region in mind, as the music pitch and tempo match the original Megadrive titles when ran in this region. However, if they are played on a chip with the tint swapped, they both have a very out of place green tint throughout various points in gameplay, which is clearly not supposed to be there, especially in Aladdin; with a red tint, both games look fine. So it's impossible to play these games properly on most emulators, as most only don't emulate the emphasis swap on NTSC region, which isn't correct for these games. And as far as I know, most of the current accurate emulators do not have an option to override the emphasis swap.

I suppose this raises a bigger issue too - there's no such thing as "the NES" or "the Famicom", or one specific "PAL NES", because there's so many different CPU and PPU variants, whether they're from Ricoh or clone chips from UMC. So you can't just emulate "the NES". Ideally, an accurate emulator would do away with just having a region select, and instead, emulate different CPU and PPU variants, and allow you to select which hardware configuration you want to use. Does anything like that already exist? I think MAME might do something similar to that with it's emulation of NES-based plug and plays.
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rainwarrior
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Re: Question about green tint on Dendy region

Post by rainwarrior »

Emulation of the emphasis bits in general has been historically poor. Mostly because they were used in so few games.

As of a few years ago FCEUX has support for 512-colour palettes, not just 64, so you can use this to produce any emphasis pattern you want. I personally added RGB PPU palettes to that project, so that we could emulate the different way those PPU variants do emphasis. I forget if there's a swapped-emphasis PAL variation in that default set, but if there isn't you might submit one.

Otherwise, sure, emulators could try to list a lot of different clone models... though there are a lot of them, and they are rather poorly documented. It can be hard for the user to know what they want in cases like this. OpenMSX or PCem, for example, have vast permutations of options for machine type and BIOS that get very confusing.

Another approach is to make options for individual features. Choose one of 3 emphasis behaviours from a drop-down list. Swap the square channel duty like on some PAL clones. Etc.
NewRisingSun
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Re: Question about green tint on Dendy region

Post by NewRisingSun »

So far, the consensus has been that all NTSC original and NTSC clone PPUs have the emphasis bits in order, and all original PAL and Dendy PPUs have the emphasis bits swapped. As SuperGame was a Taiwanese developer, and Taiwan was an NTSC country, their games were not considered to contradict that consensus, and several Russian YouTubers and streamers were known to complain about the green tint in those games on their Dendy consoles.

The truth may well be more complex than that, but I don't see a reason to put into question the current consensus given the reports that we have. A re-evaluation of the consensus should include a survey of all known clone PPUs with their emphasis behavior, and an estimate of how common they are. This wiki page may be a starting point.

In the meantime, I can add an option "Swap red/green emphasis on Dendy" PPU option, with the default setting being "enabled", to NintendulatorNRS.
Individualised
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Re: Question about green tint on Dendy region

Post by Individualised »

Maybe I'm just misremembering but I'm certain there's at least some Dendy/hybrid region PPUs that do not have the issue. Some older posts on here seem to imply that the issue was with earlier UMC hybrid chips. There's also clone PAL (not Dendy/hybrid) chips to consider.

It's strange that, disregarding the tint issue, Super Game seemed to have targeted hybrid timings as evident by the music in all of their conversions. Though it might have something to do with their titles being published by Gamtec, they may have always been intended for export rather than internal sale in Taiwan. Other Taiwanese pirate developers such as Hummer Team originally primarily focused on selling their titles in Taiwan, hence why their games target NTSC.
lidnariq
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Re: Question about green tint on Dendy region

Post by lidnariq »

Here's a possibility that just came to mind:

We know that there was a significant market for modded NTSC Famicoms in Hong Kong, using chips like the "MK5060" to convert a standard NTSC deck to PAL-B color and timing. Perhaps these games were designed to run on these specific consoles?

They should basically be identical to standard PAL famiclones, except that OAM will decay at the end of each field (edit: and the red-green emphasis swap)
Last edited by lidnariq on Tue Sep 06, 2022 9:40 pm, edited 1 time in total.
Reason: forgot to reiterate the other key difference
Individualised
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Re: Question about green tint on Dendy region

Post by Individualised »

That's an excellent point. Maybe it's even a combination of that and what I said - they modified their development console to PAL timings because they were intending to develop for PAL/SECAM regions - but they were unaware of the emphasis swap issue.
Individualised
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Re: Question about green tint on Dendy region

Post by Individualised »

lidnariq wrote: Tue Sep 06, 2022 6:19 pm Here's a possibility that just came to mind:

We know that there was a significant market for modded NTSC Famicoms in Hong Kong, using chips like the "MK5060" to convert a standard NTSC deck to PAL-B color and timing. Perhaps these games were designed to run on these specific consoles?

They should basically be identical to standard PAL famiclones, except that OAM will decay at the end of each field (edit: and the red-green emphasis swap)
Was thinking about this more. By "standard" PAL Famiclones do you mean hybrid/"clone PAL" region ones or Famiclones that try to clone the "official PAL" region (UMC did make some 2A07 clones)? If these types of mods cause the audio pitch to change as with the 2A07, then I don't think they used one of these to develop the games in that case.
lidnariq
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Re: Question about green tint on Dendy region

Post by lidnariq »

There are almost no clones of Nintendo's 2A07/2C07 - they're largely useless because they're not very compatible with preexisting 2A03/2C02 software.
Individualised
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Re: Question about green tint on Dendy region

Post by Individualised »

lidnariq wrote: Sat Sep 17, 2022 12:08 pm There are almost no clones of Nintendo's 2A07/2C07 - they're largely useless because they're not very compatible with preexisting 2A03/2C02 software.
I mean, they would be useful in countries where official PAL NES software was already widespread, but clones weren't as available in those countries for obvious reasons. The UK had a "Scorpion 8" famiclone which I believe it's advertised feature was that it could play both NES and Famicom games (or am I mixing it up with the Scorpion 16?), but I think they used a standard old clone PAL CPU for that. It wasn't completely unheard of to see imported game stuff in game retailers in the early 90s here, and reportedly some retailers even sold pirated games. Bad Influence even had a segment about the Scorpion 16 Megadrive clone. So a 2A07 clone could have been useful for the UK.

I brought up official PAL timings though because I wasn't sure if that modchip affected the APU's pitch, like a real 2A07.
lidnariq
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Re: Question about green tint on Dendy region

Post by lidnariq »

The MK5060 is used with "just" a normal 2A03 (or clone) on almost-the-normal 2A03 clock, and it's not stopped (which would create an objectionable buzz at 50 Hz since the APU is inside the 2A03)

During the NES's commercial life time, most of the clones were sold in places the NES and Famicom weren't. I believe I've read that the MK5060 originates in Hong Kong, which had easy access to Japanese software (both legitimately manufactured and not) and 2A03 compatibility was paramount there, even though TVs often couldn't accept 60Hz video.

Anything more I could say would be conjecture, so I'll abstain.
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