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#33336 - 09/05/07 07:07 PM Black bar on left side of screen (some games only)  
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Boostbaron Offline
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First of all, I just want to say what a fantastic Emulator this is.
I'm just wondering about something I've noticed on all of the NES emulators i've used so far.

On some games (say Dragon Warrior 4 or Adventure Island) there is a black bar across the left side of the screen. Usually, this only occurs during certain parts of the game (ie: Adventure Island Title screen is fine, but gameplay has the bar)

Other games (like Contra) always go right to the edge of the screen.

My NES is in storage right now, and i'm not able to test against a TV, but i'm thinking this black bar is normally outside the normal viewable area of a TV?

Does anyone have any ideas?


#33337 - 09/05/07 07:30 PM Re: Black bar on left side of screen (some games only) [Re: Boostbaron]  
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R. Belmont Offline
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That's correct - many NES games do tricks near the edges of the screen which weren't visible on CRT TVs back in the day. CRT TVs cut off between 8 and 16 pixels on all 4 sides depending on the brand and so forth - this is called "overscan". Emulators let you see the man behind the curtain so to speak.

#33338 - 09/05/07 07:31 PM Re: Black bar on left side of screen (some games only) [Re: Boostbaron]  
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AWJ Offline
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That's a feature of the real hardware. There's a hardware register that turns it on and off, which is why some games/screens (typically non-scrolling or vertically-scrolling screens) don't have the black bar and others do.

The reason for the black bar is to allow sprites to smoothly disappear off the left side of the screen, as sprite coordinates (which indicate the top-left corner of the sprite) can't be negative on the NES.

#33349 - 09/06/07 03:28 AM Re: Black bar on left side of screen (some games o [Re: Boostbaron]  
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Boostbaron Offline
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Wow, that makes perfect sense, and it's exactly the kind of answer I was looking for. grin
I've actually spent quite a long time trying to figure out what that was for, so thanks for the speedy reply!

#33356 - 09/06/07 01:21 PM Re: Black bar on left side of screen (some games o [Re: R. Belmont]  
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dvdmth Offline
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Originally Posted By R. Belmont
That's correct - many NES games do tricks near the edges of the screen which weren't visible on CRT TVs back in the day. CRT TVs cut off between 8 and 16 pixels on all 4 sides depending on the brand and so forth - this is called "overscan". Emulators let you see the man behind the curtain so to speak.

Most CRT's only cut away from the top and bottom of the NES display (they technically cut from all four sides, but the NES blanks out the left and right margins to the screen background color so none of the active region gets cut). If a game uses the left margin clip feature, especially if the background color is something other than black (SMB3 is a good example), the margin is most definitely visible on a CRT.


"Last version was better," says Floyd. "More bugs. Bugs make game fun."
#33385 - 09/07/07 09:54 AM Re: Black bar on left side of screen (some games o [Re: dvdmth]  
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Heihachi_73 Offline
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Some games even display random tiles in these areas - I think it's Pac-Man or another old Namco[t] NES game, it has a zero in the top left corner. On a CRT screen it wouldn't be visible.

Slightly away the Nintendo area, the VLC touchscreen games (video poker/slot machines) have a similar thing. Normally, the graphics fits the old CRT screens perfectly, but lately I've seen LCD touchscreens on some of them. The new screens have a large black area right around it, around an inch in size (the screens are about 15" I think).


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