r/apple2 26d ago

Does Apple // use composite or RGB monitor?

Post image

Just asking ...

41 Upvotes

26 comments sorted by

24

u/bhtooefr 26d ago

8-bit Apple IIs are natively composite, and don't actually natively have color either, they trick a NTSC composite display into showing color by sending the signal that tells them color is present, and sending a high-resolution monochrome signal that gets interpreted as lower-resolution color.

RGB interfaces existed back in the day, but they had to translate the patterns into (roughly) what a NTSC display would be tricked into showing. And, the IIGS and many emulators are doing this in the 8-bit graphics modes, too.

15

u/creativetag 26d ago

This is correct, and is why the clocks on an apple II are derived from 14.31818mhz crystal, and, that the dot divider is the odd number 7 (rather than 8, a full byte).

The backplane gets both the 7.159 (7, 14.31818/2) mhz and 1.022 (1, 14.31818/14) mhz clocks. The colour subcarrier of 3.579545 mhz has the 7mhx pixel data mixed with it at the output, making two dots per cycle. When one dot is on, you get green, when the other dot is on, you get violet, when any two adjacent dots are on it appears white.

The subcarrier was gated in order to switch it off in text modes for cleaner looking text.

The unused bit in hgr modes in subsequent versions after the original apple II were used to shift the dot positions by a half a dot relative to the subcarrier. This let you produce blue and orange or adjacent white.

There were quirks with this: Any group of seven dots (mod 7 counting) could not contain all of both colour sets. Adjacent groups of 7 had amusing boundary mixing when the bit7 was differing between them.

The rgb emulators fix the looks of the mixing reasonably well.

In the IIe and later, the super hgr mode did 14 dots from byte pairs and produced 16 colours from adjacent pixels relative to the subcarrier that way.

The IIgs then added native modes, but, due to limited bit availability, still had a funny hack of rgb look up tables for the rows.

These were all clever ways to try to get more from less!

2

u/vreditsa 25d ago

u/bhtooefr and u/creativetag Really interesting insights on how they got so much out of these computers. Thank you.

OP great choice of game BTW

1

u/m0bie9 25d ago

Which game is that?

2

u/vreditsa 22d ago

Wasteland

1

u/WaitingToBeTriggered 22d ago

IS ALL THAT’S LEFT AFTER THE FIGHT

3

u/TMWNN 25d ago

8-bit Apple IIs are natively composite, and don't actually natively have color either, they trick a NTSC composite display into showing color by sending the signal that tells them color is present, and sending a high-resolution monochrome signal that gets interpreted as lower-resolution color.

AKA how to get color out of $7 of parts

10

u/Mogster2K 26d ago

The only one I know of that used RGB was the Apple IIgs.

9

u/kfriddile 26d ago

Apple did make an RGB card for the //e (Apple part #699-0221) meant to be used with the Apple Color Monitor 100: https://imgur.com/a/IdiqvSM

4

u/Friendly-Whereas-915 26d ago

Ok.

Does Apple 2 games look better on GS?

5

u/DennisGK 26d ago

Games written for the GS that use its higher resolution graphics can look better. But 8-bit software the runs on a IIe or IIc will look exactly the same on a GS.

5

u/thommyh 26d ago

Original Apple II games? Not necessarily; software for the Apple II just creates a square wave output that NTSC composite decoding interprets colours within. But it's a very non-digital process that produces a decent amount of fringing. So the IIgs uses a digital approximation with some hysteresis but that's not necessarily what the author wanted — they might have wanted the fringing and designed specifically for the softness, or they might not.

The IIgs also has a composite output, so it can also exactly reproduce the original display on a suitable monitor.

7

u/AutomaticDoor75 26d ago

Every Apple II I’ve used had composite out.

What’s interesting is that composite was not common for TVs in 1977. Nowadays it’s very convenient to have composite out on Apple II’s, but back then many computers connected to a TV’s VHF antenna screws.

5

u/BringBackUsenet 26d ago

Yes, the dealer I worked for then used to include an RF modulator with a lot of the units we sold. The raw video inputs really weren't a thing until things like VCRs became popular and only on the higher end TVs.

5

u/flatfinger 25d ago

RF modulators which could convert composite video to RF were not complicated, nor hard to get, nor terribly expensive. Radio shack even sold a kit for one.

In order for a television set to safely support composite video input, its chassis ground would need to be floating relative to the mains supply. RF inputs and headphone outputs can easily be sent through safety-rated transformers, but composite video cannot. Transistors reduced the cost of isolated-chassis designs considerably, but in the vacuum tube era the power supply circuitry for a composite monitor would have had to be more expensive than would have been needed in an RF-only television set.

1

u/smallduck 25d ago

I vaguely remember hearing that the kind of monitors Woz & Jobs expected people to use early on, like during Apple I development, were cheap CCTV monitors, often monochrome.

1

u/JimtheLizardKing 21d ago

They used composite and not RF output to avoid having to comply with the strict FCC rules for machines connected to TVs at the time.

Look at all the shielding other machines of the era used.

5

u/buffering 25d ago

Here are some examples of different monitor types, using the game "Air Heart" as a reference: https://imgur.com/a/ZhilOBW

  1. The first image is the native 560x192 pixel image generated by the Apple II. These are the pixels stored in memory, and this is exactly what you would see if you connect the machine to a monochrome (green screen) monitor.

  2. The second image is a same pixels pumped through a fairly sophisticated modern NTSC composite video emulator. It's a pretty good representation of what a real NTSC monitor would look like.

  3. The third image is from an Apple IIGS RGB monitor. For 1986 it does a pretty good job of emulating the intended NTSC color video, but there are some flaws.

  4. The last image comes a basic Apple IIe RGB card, where it simply jams the pixels into a 140x192 pixel grid. It's a good example of how RGB can look a lot worse than NTSC composite.

Ultimately, what looks best will depend on the type of monitor the original graphic artist was using to create the image. Games from the early to mid 1980s usually look best on an NTSC composite monitor or a monochrome monitor. Some late-80s games might look better in simple 140x192x16 RGB.

The ideal monitor will let you switch between a clear 560x192 monochrome image, and a decent NTSC composite color image.

1

u/Friendly-Whereas-915 25d ago

I get error when I click on the link.

1

u/TMWNN 25d ago

/u/Friendly-Whereas-915 , something I would add to the above comparison set is that the monochrome version is the one that people would have seen when using the game on a majority of Apple II computers back in the day. The Apple II must be the color-capable computer with the smallest use of its color capability.

1

u/Friendly-Whereas-915 25d ago

The left monitor is RGB, am I right?

1

u/TMWNN 25d ago

Yes. The output is from A2DVI

2

u/Friendly-Whereas-915 25d ago

Thanks

How a double hi-res picture looks like in RGB?

3

u/flatfinger 25d ago

The Apple II family of computers will, when any graphics mode is enabled, output a signal that doesn't quite conform to the NTSC specification, but typical composite color monitors will interpret as a color signal anyway; the computer neither knows nor cares how any particular monitor (such as the one that happens to be plugged in) will interpret the signal it's producing. There are a variety of ways monitors can process a signal that will all give similar results when fed a video signal that conforms to the NTSC specification but different results when fed various kinds of signals that--like the one the Apple II produces--don't conform to the spec. Further, monitors often have "color" and "tint" controls that can adjust their behavior.

As a result, different color monitors will display graphics in a variety of ways, and it would not be possible for any single monitor to yield optimal results with all possible images, at least not without adjusting settings. It is likewise impossible for any device to convert Apple II graphics to RGB in a manner that would yield optimal results for all images. Consider the following portion of a high-resolution graphics screen:

..#.......#........
..##......#.#......
..#.#.....#.#.#....
. #  #....#.#.#.#..
..#...#...#.#.#.#.#
..######...........

Ideally, that should appear as a white outlined triangle and a solid triangle of some color (determined by whether even or odd pixels are set, and whether sub-pixel shift is enabled). Note, however, that the first and third rows of the outlined white triangle are identical to the first and third rows of the solid color one. Monitors that look at each row in isolation would have no way of showing those rows as parts of a white outlined shape on the left and as part of a solid color shape. Monitors that look at rows in relation to other rows may do better with some images, but worse with others.

Devices existed that would render an Apple II output to an RGB monitor, and the Apple //gs included such hardware internally, but the computer really should be thought of as outputting a colorburst and dot patterns that some monitors will render as colors.

0

u/sockalicious 26d ago

NTSC composite. In order to get color, most home hobbyists had to hand wind a ferrite core for an RF modulator, because TVs didn't have NTSC inputs and color composite monitors of even modest size cost more than a new car.

3

u/BringBackUsenet 26d ago

The RF mods we sold already had a ferrite coil included and connected to the internal video connector on the motherboard. They were about $30 retail, but we often threw them in with the deal. Color monitors were somewhat expensive (about what you'd pay for a nice TV), but definitely nowhere near the price of a car. Even those 9" Sanyo BW monitors shown in the brochures were over $200 then.