PAL / NTSC

[R0ger]

Well there is no need to have display list and VRAM anywhere near, I certainly never thought about it. But that's not the problem .. problem is I want to use as much as possible. 192 is safe. It's also very small number.

 

Btw. any idea how for example SNES and SEGA does 228 lines on NTSC ? Because clearly they do.

[Rybags]

Most old computers and consoles were progressive display. And they did either 262 or 263 scalines NTSC, 312 or 313 PAL.

 

Either way, you end up with practically the same display height, and number of scanlines offscreen (unless the monitor is radically underscanning).

It doesn't matter if the computer is some shitbox ZX-81, Atari, or Amiga. If it's generating that same # of scanlines then the vertical resolution will be the same. The vertical offset of display start might be different but a fat border at screen top can mean overflow at the bottom.

200 scanlines of actual generated display like C64 doesn't make a difference - the actual scanlines will still be the same distance apart e.g. of an Atari doing 240 scanlines - of course the Atari at that res will have a much taller active display.

 

So, if a NES displays 228 scanlines just fine on your TV, then no reason why the Atari shouldn't. Of course the offsets being used might screw you over but generally the good programming practice on Atari is to try and keep the top/bottom borders about the same.

Edited May 22, 2018 by Rybags

[R0ger]

So, if a NES displays 228 scanlines just fine on your TV, then no reason why the Atari shouldn't. Of course the offsets being used might screw you over but generally the good programming practice on Atari is to try and keep the top/bottom borders about the same.

 

Well I can't tell NES displays 228 lines just fine. I have no way to test it, I'm surrounded by PAL machines

I just can see that NES (well I checked SNES, but it might be the same) games, as well as SEGA games, typically have 224 (28x8, 228 was a mistake) pixels in emulators.

 

Info on misc Japan consoles (NTSC based), from quick googling:

 

NES: 256x240, but only 224 recommended.

SNES: 256x224

SEGA Master System: 256x192

SEGA Megadrive: 320x224

 

Ok, it just makes no sense ..

[Keatah]

Well, it was a US designed machine. I often wonder how much time at all went into thinking about adapting the machine to PAL. Perhaps it was a lucky hack it worked at all?

 

That being said, all the cool demos from 90s up required PAL so I gladly had my uncle ship me a machine over, and made sure to have PAL capable displays here. The only thing I have trouble with is the 50Hz CRT flicker. My eyes are incredibly sensitive to flicker, such that when I was still using CRT on PCs, I had to use 72Hz or above to not see it. I can see flicker on the new car tail lights and headlights when I move my eyes, and I believe they are > 300Hz. So at 50, I can almost see the screen turning on and off.

 

That's nothing unusual. It's more an awareness and understanding of what you see.

[Rybags]

For adapting to PAL it wasn't so bad since most old computers had the master clock running at some ratio of the colour carrier frequency.

Of course with PAL it's a 5:4 ratio vs NTSC there and the line rate is slightly different so you ended up with different frequencies usually, like with a ~ 2% difference.

 

The nice thing about the Atari is that there's the global consistency of 114 cycles per scanline but with C64 you have 63, 64 or 65 depending on TV system and oldest or newer machine which made some time critical programming a chore.

 

Not 100% sure here, but didn't the ST use identical 8 MHz clock regardless of region - plus some nice divisor tricks to get both TV systems working from the same hardware, as well as the 70 Hz mono mode (of course ignoring that the RF modulator still gave you one colourburst type but not the other).

[Level42]

This is very, very interesting.

 

An Incognito-800 + NTSC/PAL support will probably be the ultimate Atari-8bit setup.

 

That, plus a drop-in, upgrade replacement of Power - I/O board, supporting efficient DC-to-DC power conversion, on-board Lithium-ION battery port (60 watts-hour located on totally empty left-side compartment), new SIO, CF ports and DVI ports with on-board video-logic (with absolutely NO external or internal mods, other than a few signal-sample points) will be a dream come-true (coupled with a proper, external video-processor, to handle ALL video and sound outputs with the touch of a button).

 

And on the right terms, I would even consider funding this project, entirely... and build something really special.

 

Talk about leveraging the unique design advantages of the venerable 800...

All of that can be done. We should talk

[Faicuai]

All of that can be done. We should talk

 

NICE !!!

 

I will work on a decent write-up (quick summary) of the high-level specs. / goals (design-wise) and shoot them up to you, for review / consideration. We may also need FlashJazzCat wisdom, to review feasibility of developing / incorporating basic telemetry-functionality to handle or monitor power-board features.

 

As to the NTSC/PAL upgrade on A800, the board may have to be specifically designed or revised, so it connects inverted (face-down) and uses space available in-between the modular CPU-board chips, so it resides entirely on that compartment, independently... or find a way to incorporate it on the revised power-board design.

 

Stay tuned!

[Level42]

Damn I shouldn't post after a few beers....

 

Let me be a bit more realistic:

 

I could so a new PSU board with LIPO support yes. But all other is beyond my scope I'm sure. LIPO capacity is a bit overenthusiastic I think.... I have already thought about it though for a portable system....

 

For now I will need to focus on the ANTIC switch I'm afraid....sorry to have pumped your hopes......I blame Hertog-Jan.

[Faicuai]

Damn I shouldn't post after a few beers....

 

Let me be a bit more realistic:

 

I could so a new PSU board with LIPO support yes. But all other is beyond my scope I'm sure. LIPO capacity is a bit overenthusiastic I think.... I have already thought about it though for a portable system....

 

For now I will need to focus on the ANTIC switch I'm afraid....sorry to have pumped your hopes......I blame Hertog-Jan.

 

No worries!

 

But I will still send you my little "manifesto" so you can take a look at it, and if you get excited, we can also involve other bright-minds, here... it will be a very NICE project, and possibly a must-have on the (significant) 400/800 community.

Cheers!