Sprite multiplexing is a

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technique where additional sprites (moving images) can be drawn on the screen, beyond the nominal maximum. It is largely historical, applicable principally to older hardware, where limited resources (such as CPU speed and

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) meant only a relatively small number of sprites were supported. On the other hand, it is also true that without multiplexing, the sprite circuitry would be idle much of the time, and limited resources were wasted.

Description

The sprite multiplexing technique is based on the idea that while the hardware may only support a finite number of sprites, it is sometimes possible to re-use the same sprite "slots" more than once per frame or

scan line A scan line (also scanline) is one line, or row, in a raster scanning pattern, such as a line of video on a cathode-ray tube (CRT) display of a television set or computer monitor. On CRT screens the horizontal scan lines are visually discernib ...

. The program will first use the hardware to draw one or more sprite(s), as normal. Before the next frame (or next scanline) needs to be drawn, the software reprograms the hardware to display additional sprites, in other positions. For example, the

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explicitly supports hardware sprite multiplexing, where it has 64 hardware sprites, but is only capable of rendering 8 of them per scanline. On the older

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, sprite multiplexing was not intentionally designed in, but programmers discovered they could reset the

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graphics chip to draw additional sprites on the same scanline. The sprite multiplexing technique relies on the program being able to identify what part of the video screen is being drawn at the moment, or being triggered by the video hardware to run a

subroutine In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times. Callable units provide a ...

at the crucial moment.{{Citation , last=Dillon , first=Roberto , title=The Commodore 64 and Its Architecture , date=2015 , url=https://doi.org/10.1007/978-981-287-341-5_2 , work=Ready: A Commodore 64 Retrospective , pages=9–16 , editor-last=Dillon , editor-first=Roberto , access-date=2023-11-06 , place=Singapore , publisher=Springer , language=en , doi=10.1007/978-981-287-341-5_2 , isbn=978-981-287-341-5, url-access=subscription The programmer must carefully consider the layout of the screen. If the video graphics hardware is not reprogrammed in time for the extra sprites to be displayed, they will not appear, or will be drawn incorrectly. Modern video graphics hardware typically does not use hardware sprites, since modern computer systems do not have the kind of limitations that sprite hardware is designed to circumvent.

Implementations

Systems that allow the programmer to employ the sprite multiplexing technique include: *

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Amiga Amiga is a family of personal computers produced by Commodore International, Commodore from 1985 until the company's bankruptcy in 1994, with production by others afterward. The original model is one of a number of mid-1980s computers with 16-b ...

Commodore 64 The Commodore 64, also known as the C64, is an 8-bit computing, 8-bit home computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas). It has been listed in ...

MSX MSX is a standardized home computer architecture, announced by ASCII Corporation on June 16, 1983. It was initially conceived by Microsoft as a product for the Eastern sector, and jointly marketed by Kazuhiko Nishi, the director at ASCII Corpo ...

Super Nintendo Entertainment System The Super Nintendo Entertainment System, commonly shortened to Super Nintendo, Super NES or SNES, is a Fourth generation of video game consoles, 16-bit home video game console developed by Nintendo that was released in 1990 in Japan, 1991 in No ...

Master System The is an 8-bit Third generation of video game consoles, third-generation home video game console manufactured and developed by Sega. It was originally a remodeled export version of the Sega Mark III, the third iteration of the SG-1000 series ...

Sega Genesis/Mega Drive The Sega Genesis, known as the outside North America, is a 16-bit Fourth generation of video game consoles, fourth generation home video game console developed and sold by Sega. It was Sega's third console and the successor to the Master Sys ...

References

Computer graphics