RE: [stella] combat scanlines?

Subject: RE: [stella] combat scanlines?
From: Nicolás Olhaberry <nolh@xxxxxxxxxxxxx>
Date: Fri, 4 Jan 1980 07:06:21 -0300
----- Original Message -----
From: ben <ben@xxxxxxxx>
To: <stella@xxxxxxxxxxx>
Sent: Saturday, November 03, 2001 8:43 PM
Subject: [stella] combat scanlines?

> Can someone please let me know how many visible scanlines Combat assumes
> display the entire playfield and scores?

Since VBLANK ends on line 36 and VSYNC starts on 260, a combat frame has 224
visible scanlines. How many are really visible on a TV, I´m not sure. I´ve
read on this list (if I remember right) that the newer ones can display up
to 210 atari lines on NTSC.

> I have tried everything, and am pretty sure Combat assumes the Overscan
> area is *visible* (ie needs to show 40-261, not the expected 40-231).  Is
> this true?

I haven´t played combat on a real atari for at least 10 years, but I don´t
remember that the bottom border was that thick, it was pretty much the
same size of the upper border. So, I think they expected that the last
lines of the frame will fall in the overscan area.

> How many scanlines are you emu authors showing, and is it always constant
> for every cart/machine?  What happens with PAL/NTSC?

I don´t know for sure in which scanline the visible screen starts or stops,
and maybe that changes with the TV set too. So, the simpler solution from a
emu point of view is just to display every line with the VBLANK register
turned off. Most of the games on NTSC don´t have more than 200 of those,
just a few like combat use a little more. So, you can have a big bitmap
with, let say, 256 lines to be safe, and show just a portion of it, using a
resolution like 320x200 or 320x240 for the "taller" games.



Archives (includes files) at
Unsub & more at

Current Thread