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– At least in the Tandy 1000 version (not sure about the PCjr), the original King’s Quest and the following AGI games use the 320×200 resolution to display the 160×200 graphics, although the PCjr and Tandy 1000 machines feature a native 160x200x16 graphics mode. Why was this move taken, as it consumes more memory and makes the games slightly slower since twice as many pixels must be written? Was it to display the more-easily-readable 320×200 font?
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Hi Vincent, I have mucked around with the AGI games and written tools to extract the graphics from them and turn them into javascript stuff, so I know a bit about what goes on underneath.

The graphics take the same amount of space whether it is 160×200 or 320×200. Each pixel in the 320×200 graphics modes used in the AGI PC games simply is drawn 2 pixels wide. The AGI engine doesn’t store graphics as bitmaps, but drawing instructions – such as draw a red line from (0,0) to (100,100) then a circle etc. So I don’t think size was a problem. And since the screen is drawn once when it is loaded, speed wouldn’t have really been affected much either no matter what mode. Maybe it is just that the 320×200 mode is far more common (e.g. supported on CGA PC, Tandy and PC Jr).

Also of note to people interested in this is that it was possible to hack standard CGA colour card/RGB monitor setups (the four colour cyan, magenta etc setup) to display 8 or 16 colours at 160×200. If Sierra had known about this back in the day, there could’ve been a driver to get 16 colour AGI games running on CGA! This is probably most interesting to those who had to struggle through the AGI games with CGA (like me!).