CGA 16 Color Graphics Part 1 - Icon Demo & Styx

Channel:

Nerdly Pleasures (Great Hierophant)

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Published on July 16, 2021 6:05:12 AM ● Video Link: https://www.youtube.com/watch?v=FqA6jTq_fPM

Game:

Styx (1983)

Duration: 5:27

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Thanks to my new RGB2HDMI I can capture all sorts of weird video modes, including the text modes masquerading as graphics modes for the IBM CGA. Here I start with the Icon Demo, which only runs on a CGA or 100% compatible. Because it relies on text characters, only looks right on an IBM CGA card. Clone CGA cards may and Tandy 1000 graphics adapters run the demo, but the graphics will look different in places because they use slightly different character glyphs than IBM did. In this demo, both 40-column and 80-column modes are used to display graphics, each being cut down into 8x2 pixel cells with two colors per cell. The top two rows of all 256 ASCII and extended ASCII characters in the IBM's Character ROM can be used in these modes, allowing for more detail. This technique was later used in the games Icon: Quest for the Ring and 7 Spirits of Ra, but they have some support for EGA.

Next I demonstrate Windmill Software's classic QIX knock off, Styx. Styx uses an 80-column text mode cut down to an 8x2 cell size. Then each cell uses a text character which occupies one half of the cell, allowing a color to be assigned to that character and another color to be assigned to the remaining space for a total of two colors per cell. The effective resolution of this mode is 160x100 pixels, but it permits display of all 16 CGA colors on the screen instead of the normal 4-color or 2-color graphics modes.

Styx has been very difficult to capture because Windmill Software reprogramed the 6845 CRTC on the CGA to use rather capture-device unfriendly values. The Datapath E1s could not capture it with the video fed directly to it via a DAC, but the RGB2HDMI can display it. However, the RGB2HDMI requires a special setting to avoid the constantly flashing screen shown when the title screen transitions to the gameplay screen. I fixed that just after the gameplay screen finished drawing itself, it should not flash like that and can be avoided in the future by adjusting the setting on the title screen. You might want to compare the original IBM version of Styx to the IBM PCjr. version of Styx also captured on this channel.

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