Odd lines on the side of the screen

[johnnystarr]

I haven't come across this in any of my projects, so I'm not sure exactly what would cause this. I have a screenshot here of a ROM that has these odd lines down the left side. I've noticed quite a few 2600 ROMs have odd graphics quirks like this.

 

Does it have something to do with the original code not running correctly in emulation? Or, did the developers just throw their hands up and go "oh well" and the actual games looked like this?

[shazz]

Isn't it the HMOVE blanking enabled in Stella (Alt+M) ?

[SeaGtGruff]

Isn't it the HMOVE blanking enabled in Stella (Alt+M) ?

Yes, those are the well-known "HMOVE lines." There's a way to move the sprites without getting the HMOVE lines by doing a "cycle 73 HMOVE" or "cycle 74 HMOVE," but if you do that then you can move the sprites only to the left. These HMOVE lines are actually what allows you to move the sprites to the right.

[iesposta]

Yes, the actual games looked like this.

Some, like Activision, do an HMOVE on every line, so the whole left side (strip) from top to bottom, is black.

When programmers wanted to use the whole screen, like Ms. Pac Man, they can be seen.

As stated above there is a trick to eliminate them.