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View topic - Cosmic Spacehead emulation problems (graphical hiccough)

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  • Joined: 12 Apr 2005
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Cosmic Spacehead emulation problems (graphical hiccough)
Post Posted: Tue Aug 18, 2009 6:47 pm
I have a problem with the emulation of the SMS/NTSC version Cosmic Spacehead - the top of the screen flickers as if the horizontal scroll register is not being set on time (screenshot). The problem seems related to the amount of stuff on screen at the time; when the cursor is hovering over an object on the screen and some text is displayed to describe it, the height of the incorrect band increases.

If I run the emulator in PAL mode, the glitch vanishes. Emukon demonstrates a similar glitch. MEKA can be forced to display the glitch if you boot the ROM in PAL mode then switch to NTSC whilst it's running, which suggests that the game may be detecting the wrong TV system in my emulator (though if I start in PAL then switch to NTSC in my emulator I have the same problems).

Has anyone else had similar issues, and if so have they managed to fix them?

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  • Joined: 26 Aug 2008
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Post Posted: Tue Aug 18, 2009 10:45 pm
It happens in RetroCopy also. The game was tested pretty much exclusively on PAL consoles, and the 224 line mode likely never existed in the US market in any sort of quantity. The fact the game doesn't even work on european SMS1 without the VDP upgrade should tell you how much it was tested... ;)

With 262 lines vs 313 there simply cannot be as much done in the offcsreen area as you increase the screen size. Which is likely why it seems to differ depending upon what's on the screen.. I'd guess.
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Post Posted: Tue Aug 18, 2009 11:30 pm
That may also explain how the Game Gear version works, as the screen is cropped.

Does this mean that the PAL version is the "correct" one? The game doesn't appear to compensate for framerate differences, but I notice that the game apparently was released in the USA...

(PS: Thank you attachment fairy). ;-)
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Post Posted: Wed Aug 19, 2009 1:50 am
benryves wrote
That may also explain how the Game Gear version works, as the screen is cropped.

Does this mean that the PAL version is the "correct" one? The game doesn't appear to compensate for framerate differences, but I notice that the game apparently was released in the USA...

(PS: Thank you attachment fairy). ;-)


I find it hard to believe cosmic spacehead was released in the USA, it was a late SMS game and by then the USA was a dead market. Maybe someone got confused with a megadrive version? The issues in the game are hardly "that bad" though, at least from my brief look, I mean you look on the NES side and glitchy graphics are actually in every game almost, and people seem to like it. And like you said, the gamegear which is NTSC would have cropped out all those issues making it unimportant.

You also have to remember when running MEKA is it's goal is to make games as easy to play as possible, so check out the patch file to make sure any game doesn't have a patch, and the other config files to see if a game is forced to a certain region when you compare your emu to it.
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Post Posted: Wed Aug 19, 2009 4:59 am
I know NES had really glitchy scrolling, though overscan on NTSC TVs (no idea on PAL) would have covered much of it, so I guess they didn't really think it was worth the effort.
Could it be the same here?
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Post Posted: Wed Aug 19, 2009 9:00 am
I'm pretty sure it wasn't released in the US. Someone with the game and an NTSC console can confirm the glitchiness.
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Post Posted: Wed Aug 19, 2009 12:38 pm
PoorAussie wrote
I find it hard to believe cosmic spacehead was released in the USA, it was a late SMS game and by then the USA was a dead market. Maybe someone got confused with a megadrive version?

I'm not sure - it was on the Internet, so it must have been true. ;-)
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You also have to remember when running MEKA is it's goal is to make games as easy to play as possible, so check out the patch file to make sure any game doesn't have a patch, and the other config files to see if a game is forced to a certain region when you compare your emu to it.

I can't find any reference to it in MEKA's patch database, but have modified my "quick load" code to switch to PAL if the game uses the Codemasters mapper, runs on the Master System and doesn't have a country explicitly set - this seems to have done the trick.

The NTSC overscan seems to be another plausible answer. Thanks, all!
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Post Posted: Wed Aug 19, 2009 4:17 pm
benryves wrote
PoorAussie wrote
I find it hard to believe cosmic spacehead was released in the USA, it was a late SMS game and by then the USA was a dead market. Maybe someone got confused with a megadrive version?

I'm not sure - it was on the Internet, so it must have been true. ;-)

It was a (fairly) quick and dirty hack of a NES game released in the US, hence the crappy 3-colour sprites.
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10-year bump!
Post Posted: Mon May 20, 2019 9:00 pm
Can you guys tell me if there is a way to play this game on retroarch without it being executed as a PAL game ?

The S8DS emulator from Flubba emulates the game in a NTSC framerate and it's much more nice to play, but I failed to configure any cores on retroarch (in my cellphone) which could play this game in NTSC speed.

Thanks.
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Post Posted: Mon May 20, 2019 10:33 pm
An accurate emulator can't do that. What you want is effectively an overclocked system, running with enough cycles per frame to avoid the glitch but then also at 60Hz.

Consider that this game was designed for 50Hz - kind of. The N*S version did come out in the US bit I'd guess it ran faster than intended. It was written in the UK and the SMS version was only tested on PAL SMS2s....
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Post Posted: Mon May 20, 2019 10:36 pm
Alas, will have to finish it on my DS instead of my cellphone! Thanks for the info.
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