[viler]

To me it seems like PC emulators tend to use the wrong approach with CGA. It's a fixed-frequency standard, so in principle it shouldn't be all that different from what you see in a typical emulator for the C64, Amstrad CPC etc.: the frame is rendered at a fixed resolution and refresh rate, just as the monitor or TV would display it (overscan area included!); the size and positioning of the active raster within that area are determined by the timing parameters sent to the (emulated) display controller.

In an emulator like DOSBox, only the active raster is rendered, and it attempts to dynamically work out the H/V refresh and aspect ratio. Maybe for historical reasons, since it was originally meant for emulating VGA on a VGA monitor. Same goes for 86box, PCem and MAME... although at least the first two do somewhat better with this demo.

[bombcar]

The PC world quickly became “the subset of features that work on PCs and clones” which means that shortcuts are often taken - both in clone development and emulators.

Whereas something like the NES had defined hardware that was mostly identical and so if some feature existed some game somewhere used it.