Display: 560x192

Software concept

Apple's Double Hi-Res mode. 16 colors but must be used skillfully due to artifacting.


The first video game about Display: 560x192 was released in 1979.

Sierra On-Line, Epyx and Data East has published most of these games

The double hi-res mode is a bit of a technical nightmare to use. Older Apple hardware, the original ][e or eairlier, must have an 80-column card upgrade _and_ a modification to the card and motherboard. So the ][ enhanced (motherboard Rev. B) and later models are really the only models double hires games are intended for (][gs systems also). The way it works is compressing the normal motherboard video ram contents to the left half of the display, compressing the video ram on the 80-column card to the right half of the display, forcing a bank-switch about halfway through a scanline, and bank-switching back before the next scanline. That is "_about_ halfway" because it varies per line due to quirks caused by Woz' minimal chip and memory use designs. In 280x192 resolution, it takes a full pixel made of various colors to produce the desired color of 6 total colors (hardware limit). In 560x192 mode, that same dezired color only uses half of a pixel (left half or right half). So the colors needed to produce the desired color may not be there. This means specifing 'green' on a pixel will make a different color than 'green' on the neiboring pixel (and neither one will actually be green on most pixels). It is as if each pixel uses its own pallette. This is both a disadvantage and an advantage. Disadvantage because of the.complexity needed to get the desired color out of each pixel. Advantage because the hard limit of 6 colors fed into the mode can produce up to 16 colors depending on exactly when and where the color is placed in memory. The 'map' of memory banks, color, pixel, and timing relations is complex but does not change. It can be learned by an artist or handled by an algorythm. But implimenting the picture data though this map means using up to 96 times as much CPU power. I think no system ever had more need of a GPU here.