RGB and the Apple II

["Joel" <joelbuckley54.nospam.@hotmail.com>]

Apple II and RGB Video

By Joel Buckley 11/7/2002

There have been a number of questions related to RGB video on the //e, //c,
and Laser 128.
I could only find limited info on these topics in the FAQs, so I thought I'd
add what I have in my notes and references. I offer no guarantee that this
is 100% accurate.

In the Apple // series of computers, there have been 15 pin video ports on
the Apple ///, Apple //e (option), Apple //c, Apple //c+, Laser 128, and
Apple IIgs. Despite all using a 15 pin connector, most of these ports are
different and incompatible!

RGB may provide crisper, higher resolution displays than televisions or
composite video displays.
But RGB is not one standard. RGB monitors may use different frequencies,
digital #s of colors (8 color, 16 color, or analog) and different sync
encoding (separate vertical and horizontal sync, or composite sync, or sync
mixed with the video signal).
Early IBM computer used a type of RGB display which they called CGA. It is
16 color, RGBI (Red,Blue,Green,Intensity) and runs at 60Hz vertical 15KHz
horizontal scan rate. These frequencies are the same as a regular TV set.
The Apple II family uses these same frequencies. Later, higher resolution
monitors, like EGA and VGA, use higher scan rates and generally are not
compatible with the Apple II series.

I think the Apple /// was one of the earliest versions of RGB for the Apple
II family.
Here's the pinout:

Apple ///
1. Shield Ground
2. Green
3. Comp Sync
4. N/C
5. Red
6. Ground
7. -5v
8. +12v
9. Blue
10. Intensity
11. NTSC B+W
12. NTSC Color
13. Ground
14. -12v
15. +5v

(I don't have an Apple /// and have not verified this myself.)

The Apple //e had an RGB option which was very similar to the Apple ///. I
actually have 2 of these boards (though I haven't hooked them up to an RGB
monitor.)  I believe it was called the AppleColor 64k 80 column card. The
identical card was sold by a company called Video 7 (maybe they developed
it?) They were not that much different from the early big 64k/80 column
cards. They had a 16pin ribbon cable connector on top (which connected to a
DB-15 connector). The matching monitor was called AppleColor 100,

The pinout is basically a subset of the Apple ///.
Apple //e

1. Shield Ground
2. Green
3. Comp Sync
4. N/C
5. Red
6. Ground
7. N/C
8. N/C
9. Blue
10. Intensity
11. N/C
12. N/C
13. Ground
14. N/C
15. +5v

I believe some of the memory expansion cards for the //e made by Applied
Engineering also had an RGB option. I don't have any information on them.

The Apple //c and //c+

They also had a video expansion port which did not directly do RGB. The port
could drive an LCD display (very rare). It also carries composite video and
sound, so some adapter cables plug into it for those-but these are not RGB.
There was an adapter made by Telemax called the Peacock model CM2C that
converted these signals into RGB. I do not have one of these.

Apple //c, //c+

1. TEXT
2. F14M
3. COMP SYNC
4. SEGB
5. SOUND
6. LDPS
7. WNDW
8. +12v
9. PRAS
10. GR
11. CGSEROUT
12. NTSC (Composite video)
13. Ground
14. VIDD7
15. CREF

Laser 128

This was an Apple //c clone. But its video port differs from the //c. While
I believe it may work with the //c LCD display and with adapter cables that
split out composite video and sound, it also has the signals needed for an
RGB display without any extra circuitry.

Laser 128

1. INTEN
2. F14M
3. RED
4. BLUE
5. SOUND
6. LDPS
7. DSPEN
8. +12v
9. HSYNC
10. /CSYNC
11. CGSEROUT
12. NTSC (Composite video)
13. Ground
14. VSYNC
15. GREEN

Then there was the Apple IIgs. While it uses the same frequency monitor as
the others, it uses analog video signals with superimposed sync signals.
Besides its own monitor, it was compatible with a few other brands.

Apple IIgs

1 Signal ground (Red)
2 Analog RED with sync
3 Composite sync
4 No connection
5 Analog GREEN with sync
6 Signal ground (Green)
7 -5 volts DC
8 +12 volts DC
9 Analog BLUE with sync
10 No connection
11 Sound 1V peak-to-peak
12 NTSC/composite color video out
13 Signal ground (Blue)
14 No connection
15 No connection

In general Color monitors designed for the Macintosh have higher frequencies
and aren't compatible with Apple II computers. There are exceptions to this.
I believe there was a VGA board for the IIgs called Second Sight. Then there
are devices called scan doublers, which may let Apple II video be displayed
on some monitors which operate at twice the frequency as the Apple II.

IBM CGA RGB Monitors

I present this information because these monitors were once fairly common
and you may want to try to hook them up to your Apple. Sometimes the Apple
provides Composite Sync and the IBM wants separate Vertical and Horizontal.
You can build a circuit to split them apart. But first try running the
composite sync into both. Sometimes it will work. Trying to make one of
these work with a IIgs is probably more trouble than its worth, especially
with IIgs monitors from school surplus being a dime a dozen. Trying the
reverse, getting a Iigs monitor to work with a //e or Laser 128 is also
rather complicated.  But wiring a CGA monitor to Apple ///, //e with RGB
output, or Laser 128 may be doable with just a cable.

Perhaps even more common than CGA monitors, were monochrome digital (MDA) or
TTL or Hercules compatible monitors. These used a 9 pin connector very much
like the CGA, with monochrome Video output on pin 7 (Red,Green,Blue unused).
Intensity was used. These monitors worked at 50Hz vertical, 18KHz horizontal
instead of 60/15Khz. Many PC clones could provide either of these video on
the same connector.

And I even have an odd hybrid, a CGA mono, which takes RGBI at 60/15K and
displays it greyscale on a mono monitor.

IBM CGA

1. Shield Ground
2. Ground
3. Red
4. Green
5. Blue
6. Intensity
7. Mono (not CGA)
8. Horizontal Sync
9. Vertical Sync


Some additional comments:
Improvement with the digital monitors may not be as much as you would
expect. The Apple does some tricky things with color and video in its high
res and double hi-res modes. These don't always translate well into digital.
The AppleColor composite monitor gives a pretty good picture. It also has a
black and white switch which can improve the display quality on text and
monochrome graphics. The Laser 128 has a mono/color switch which can often
improve the display for text and graphics when set to mono.
I believe the Apple digital monitors are a little bit different than the IBM
type. They use something called XRGB or linear-weighted summing. Standard
RGB actually has bright and dim versions of 8 colors. The Apple produces 16
(or 15) different colors. Many are the same on both, but not all.