Max. NTSC resolution of ATARI 8 Bit and 2600 ?

[Lord-Chaos]

I´m working on a PAL ATARI 800 XL.

 

On a PAL TV , it´s possible to display up to 239 lines , on my TV.

 

If you use more than 239 lines,the TV will produce strange effects ...

 

Now how many lines can be displayed on an NTSC TV - how much overscan can I use without making a game unplayble for NTSC users ?

 

The max. horizontal resolution seems to be 344 pixels on my system , it may be more with other monitors/TVs ...

 

Anyone knows about ATARI 2600 resolution on PAL or NTSC systems ?

 

NTSC games seem to look the same on my console,except the wrong colors (blue instead of green etc.).

 

Thimo

[DEBRO]

Now how many lines can be displayed on an NTSC TV

Atari recommended 192 scan lines for a visual display. This would make sure the screen would fit on all NTSC TVs. You should be able to get away with at least 200 visible scan lines without a problem. Most modern TV's can handle this with no problem. Atari's 192 scan line recommendation was very conservative.

 

Anyone knows about ATARI 2600 resolution on PAL or NTSC systems ?

On Stella Atari recommends the scan line count should be PAL 312 (3-VSYNC/45-VBLANK/228-Kernel/36-overscan) and NTSC 262 (3-VSYNC/37-VBLANK/192-Kernel/30-overscan). Again, you should be safe doing 200 visible lines for NTSC. You would adjust the VBLANK and overscan times to compensate for this.

[EricBall]

The critical items are the total number of lines NTSC:262 PAL:312 (particularly PAL which will go black&white on an odd number of lines) and 3 lines of VSYNC (turning VSYNC off & on right after WSYNC). Emulators are typically more tolerant of the incorrect number of lines than TVs (use Z26's video mode #9), though some TVs may handle a bad number of lines.

 

It's also important to use a consistent number of lines (especially when changing kernels), or the screen will jump.

 

For Skeleton+ I added 11 lines for the counters (NTSC:201 visible, PAL:239 visible) and it displays fine on my ancient 20" Zenith. I just adjusted the timers I use for vertical blanking.

 

Horizontal resolution is fixed. The 2600 has 160 onscreen pixels. The 7800 has 320 pixels (but 160 pixel positioning).

[mos6507]

I would also recommend 200 pixels.

 

I once experimented with overscan on the 8-bit and found that anything over 200 pixels would get lots in overscan in the 4 corners depending on how rectangular your tube is.

[Thomas Jentzsch]

I once experimented with overscan on the 8-bit and found that anything over 200 pixels would get lots in overscan in the 4 corners depending on how rectangular your tube is.

So using a centered score display in that area should work, right?

 

BTW: Are modern NTSC TVs still not rectangulare?

[EricBall]

A typical (non-HDTV) NTSC or PAL tube is has a nominal aspect ratio of 4:3 (aka 1.33). However, the picture often goes beyond the edges of the screen (overscan). This sometimes can be adjusted, though not necessarily by the owner.

 

There is also no true specification for how much of the TV signal is picture versus blanking. The DVD (NTSC) spec of 84% (720/858) horizontal and 91% (480/525) vertical is probably close to the maximum. Compare this to the 2600/7800 standard of 70% (160/228) horizontal and 73% vertical (192/262).

 

This all can be extremely frustrating when trying to draw a true circle or square on a standard TV.