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I am using Nestopia on Windows Vista (64 bit version of Vista). Every game works great except Super Mario Bros. 3.

Here are the problems:

1. There is a vertical, sky-blue colored strip on the left side of the screen on any level. (Not there when viewing the maps between levels)

2. When making Mario run or walk there is a another, more narrow, vertical strip (on the right side of the screen when moving forward or on the left side of the screen when moving in reverse) where the colors and shapes do not match what is supposed to be in those strips.

3. There are moving pixels that are mostly sky-blue colored on the left side of the screen that aren't supposed to be there in-between the bottom of the ground and the top of the information bar on any level.

Thanks for reading and any help would be appreciated.

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Those all happen with the real cartridge on real hardware. You just may not have noticed because your TV wasn't as sharp as a computer display and TVs typically "overscan" the image so between 8 and 20 pixels are off the edges of the screen on each side.

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O.K. Thanks for the help.

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To be technical:

1. SMB3 uses a feature of the NES that "clips" the left 8 pixel columns of the video display. These pixels are drawn using the current screen background color (in general, the color of the sky in levels that take place outside). This is done to allow smooth sprite scrolling off the left side of the "playfield" portion of the screen, as well as to minimize the visual artifacts caused by the 2D scrolling (see below).

2. SMB3 supports two-dimensional scrolling, even though there isn't enough VRAM to support it "natively." As a result, the contents of the screen that scroll off the right edge will "bleed" into the left side of the screen and vice-versa. Although the bleeding is mostly invisible because of the 8-pixel clip mentioned above, the effect is still visible in the color scheme used to draw the background graphics (each entry in the NES's color table works on a 16x16 region of the screen, which is wider than the 8-pixel margin). Note that many games that scroll in both directions choose to map the VRAM differently, causing the artifacts to appear at the top and bottom of the screen instead (which is much less likely to appear on a TV, due to the NES's resolution being "taller" than the TV's actual dimensions).

3. To display the status bar at the bottom of the screen, the game uses a special "raster" effect to change the portion of VRAM to be displayed (as well as which character ROM banks should be used as the graphics source). The game has to disable video output temporarily to do this (which is why there's a 1-pixel horizontal line between the playfield and the status bar). However, due to timing issues (especially when certain sounds are playing), SMB3 is unable to turn on the display in time for the first few pixels of the status bar to display properly.

Other glitches show up in other parts of the game, such as the Spade game (not the N-Spade one). Look closely at the left/right edges and you might notice them as you play.


"Last version was better," says Floyd. "More bugs. Bugs make game fun."

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