Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A raster interrupt is a computer interrupt signal that is used for display timing purposes. It is usually, though not always, generated by the system's graphics chip. Often, the graphics chips used in home computers and video game consoles during the 8-bit era were somewhat limited ...Full description
Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A raster interrupt is a computer interrupt signal that is used for display timing purposes. It is usually, though not always, generated by the system's graphics chip. Often, the graphics chips used in home computers and video game consoles during the 8-bit era were somewhat limited in their capabilities. For instance, the MOS Technology VIC-II chip used in the Commodore 64 could only handle eight sprites simultaneously. Raster interrupts were sometimes incorporated into these video chips in order to allow skilled programmers to transcend these limitations. An interrupt would be set to trigger when a given screen line was refreshed, and the interrupt routine could then reload the chip's registers. In doing so, multiple graphics modes could be mixed on one screen, the number of sprites could be greatly multiplied, and a portion of the screen could be scrolled while another part remained stationary.