
How CGA Graphics worked [video] - Jerry2
https://www.youtube.com/watch?v=BsDssW5dIqM
======
johansch
This wouldn't be complete without mentioning the enhanced CGA version a lot of
Europeans experienced via Amstrad/Schneider PCs in the 80s (they tended to be
the cheapest way to get a PC here, back then).

"The Amstrad used an "enhanced" CGA graphic mode, which could display 640x200
pixels with 16 colors (or grayscale)."

[http://www.old-computers.com/museum/computer.asp?c=183&st=1](http://www.old-
computers.com/museum/computer.asp?c=183&st=1)

[http://www.nostalgianerd.com/amstrad-
pc1512](http://www.nostalgianerd.com/amstrad-pc1512)

There were probably at least five pieces of software released which supported
this mode. :)

The PC1512 came bundled with the GEM windowing system from Digital Research,
including a paint program:
[http://www.reenigne.org/computer/gempaint.gif](http://www.reenigne.org/computer/gempaint.gif)
as well as a fairly state of the art graphical BASIC:
[http://www.reenigne.org/computer/basic2.gif](http://www.reenigne.org/computer/basic2.gif),
[https://www.youtube.com/watch?v=dDL8w_Mi49A](https://www.youtube.com/watch?v=dDL8w_Mi49A)
(video in EGA though).

~~~
songshu
Ah GEM and Basic 2 Plus! My parents wrote a retail system (cashier, stock,
orders) for their store with this and it's still running today (via DOSBox,
the hardware is long gone)

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adrusi
This link is dead.

I assume this is the same video.

[https://www.youtube.com/watch?v=niKblgZupOc](https://www.youtube.com/watch?v=niKblgZupOc)

------
pdkl95
Speaking of CGA... did you know that an IBM PC 5150 (4.77 MHz Intel 8088) with
a CGA card can display full framerate video?

[http://trixter.oldskool.org/2014/06/19/8088-domination-
post-...](http://trixter.oldskool.org/2014/06/19/8088-domination-post-mortem-
part-1/)

This is accomplished by _compiling_ the video into _branch-free code_ that
sends minimal updates to the CGA.

~~~
userbinator
The same demogroup did this around a year later:

[https://news.ycombinator.com/item?id=9338944](https://news.ycombinator.com/item?id=9338944)

[http://8088mph.blogspot.com/2015/04/cga-in-1024-colors-
new-m...](http://8088mph.blogspot.com/2015/04/cga-in-1024-colors-new-mode-
illustrated.html)

------
Lerc
I often thought that CGA could have been much better with very little change
at the hardware level.

If the colour displayed onscreen had the red level inverted the options would
have been much more erm... palatable.

For an output of (1-r,g,b) you would get some lovely options
[http://i.imgur.com/rMAr9mU.png](http://i.imgur.com/rMAr9mU.png)

If done at the Digital level flipping the R line of the RGBI You would remain
in the standard 16 colours but with better combinations

[http://i.imgur.com/2AWs9E7.png](http://i.imgur.com/2AWs9E7.png)

You get a nice blue gradient palette and an earth tone palette (brown,black
and green).

~~~
takeda
Yes but wouldn't 16 colors in composite mode look worse then?

It seems like these colors were chosen exactly because when you mixed them you
would get nicer colors.

~~~
ajenner
The video is a bit misleading here - most CGA composite games didn't use the
2bpp mode at all but instead used the 1bpp mode. This gave 15 reasonably nice
colours distributed roughly evenly through RGB space, and was also more
consistent between different versions of the CGA card.

------
rwmj
TIL: dosbox can emulate CGA composite mode.

Of course, Hercules Graphics Adapter is the one true graphics adapter :-)

~~~
pdkl95
CGA 4-color mode was extra "fun" after SIMCGA munged it to black and white
pixels with a different aspect ratio.

------
brandonmenc
Great video, but missing from the palette discussion is the cyan-red-grey
option, which was by far the best one and only used in a handful of games.

Be sure to check out the game Round 42 for another great demonstration of the
160x100x16 mode.

I had access to that Tandy portable - it had the WORST screen ever, but for
some reason I have a soft spot for it.

~~~
mysterydip
Round 42! What a blast from the past. I don't know how well-known that game
is, but when it ran (on our IBM PCjr with the memory expansion), it was great
fun and a graphical treat (for the time).

~~~
T-hawk
Another Round 42 fan here from way back. This was one of the first of original
PC games to start failing on newer hardware; even most VGA cards weren't
compatible with that funky CGA mode. I wonder if Dosbox can handle it at
all...

