Video encoding "formatting frame"

[Yuan]

Hi. I'm a new member and I'm not sure if this is the correct place to post this, but here it goes:

The video signal of some consoles, particularly some of the older ones, have a "formatting frame" or something and the image "space" isn't filled completly.
On some like the Mega Drive/Genesis or Famicom/NES, it is the background color of one of the scrolling grounds. On others like the Super Famicom/Super NES it's black. (You can see what I'm talking about if you hook your console to an ATI video card, a new flat-screen TV, or something.)

I presume that these consoles have this thing because older TVs were kinda round cornered, and/or didn't display the entire screen, not showing some of the signal.

What I'd like to know, is wether the extra frame is added by the video signal processor of these consoles, or if the processor receives it like that directly from the CPU (would be my guess), because cartriges don't seem to include this information, except on some exceptions like StarFox or Street Fighter games where they have a programmed frame (but the "default" frame is added anyway).

The funny thing's that I noticed (my) output video cards have similar frames when connected to a TV, which made me think it could be the signal processor.

Well, that'd be my question, hope someone can answer it! Thanx for your time.

BTW, I know it's got nothing to do with this, but:

1 Can you play backed-up CD games on an unmodded Neo Geo CD/CDZ?
2 Is there NO WAY to get a decent video signal out of the Famicom/NES, or is it just too much complicated?*

*The NES's composite mess of a signal's probably a well-known disaster, on mine the pixels won't even crawl, they just hang! Talk about lousy signals!
Someone probably did something about it already...
... or at least tried...

[Vertigo]

Wellllll, on the Megadrive the border colour changes according to the action, so it must be programmed into the game somewhere in order to do it, or maybe the console just receives it as a certain colour in the palette. You can see it in action on Sonic and also ThunderForce IV where the boss alert sounds and the border colour cycles through.
It must be to do with a certain colour in the palette. So open up a palette display in an emulator and see which it it, and if it's the same in a few games then it must be a default in the hardware. Possibly?