NES Games With Lowered Resolution? Garbage Area?

[NayusDante]

I've always wondered about some of the odd quirks of the far left and right sprite columns in NES games. On the left, I've noticed that some games use the far left 8-16 pixels, but others leave it black. For example, Mega Man 1-2 fill this column, but 3-6 do not. Other games fill the area with colors other than black. I'm assuming this is to reduce draw calls and improve framerate, but is there a different reason? On the right side of the screen, many games exhibit random tile placement that doesn't line up with the actual map data or palette, but this is outside the overscan of most CRTs. I've always wondered if there's any rhyme or reason to this area, if the arrangement of random tiles implies anything about what's loaded in RAM.

Have either of these things been documented or explained?

[ccovell]

It's been well-documented and explained, so don't worry.

See the bottom of this page: http://wiki.nesdev.com/w/index.php/PPU_attribute_tables

So for one, the tiles are not random on the sides of the screen, but the colours might be (since colour attributes are 16x16 in size, but tiles are more detailed at 8x8.)

For another, the leftmost 8-pixel column can be selected to show tiles & sprites as normal, or to hide them, both to hide this attribute artifact a little bit and to eliminate sprite pop-up when they appear from the left on-screen. Many consoles have to deal with these problems in one way or another.