activision centering

[taylorcomm]

I noticed today that a lot of my activision games were really off center on the tv. Mostly to the right, I plugged it in two different tvs and it was off center on both. Is it just me or is this something typical I usually just overlook?

[Bryan]

On some games the left edge of the playfield is left black to hide the "combmarks" made by doing an HMOVE in mid-screen.

 

-Bry

[taylorcomm]

Thats interesting, on some the right side is cut off too, like in stampede.

But on others not only is it off center to the right, but it also seems there is more black space on the top than the bottom

[Thomas Jentzsch]

Thats interesting, on some the right side is cut off too, like in stampede.

This was probably done to let the cattle smoothly (dis)appear behind the blacks bars without wasting precious CPU cycles for doing HMOVE every scanline. This trick works only for games that don't use the blocky playfield graphics.

 

But on others not only is it off center to the right, but it also seems there is more black space on the top than the bottom

It is completely up to the programmer where the visible screen should start and stop. Maybe he needed some connected extra cycles for off screen calculations and therefore shifted the screen slightly down.

[The MilkMan]

Thats interesting, on some the right side is cut off too, like in stampede.

 

I don't know if a single VCS may be the problem. I have a second 2600 as a back-up, but I hardly ever use it because it produces a "white noise" in the volume when its on, and all the games are shifted the right alot. My main VCS does not produce any of those symptoms. ?

Don't know if it's the system or a simple hardware problem I'm not aware of.

 

Oh, and Stampede...I just plunked down about 4 hours of play last night on that one.