Fonts that use a 256 character space for all characters. These typically have a standard ASCII set of characters and control spaces for the lower 128 positions, and a unique set for the upper 128. These 8-bit fonts were thus sometimes referred to as "extended ASCII."
Due to and the fact that different characters, or the same characters in different positions occupy the upper 128 positions (and occasionally even some of the lower 128), 8-bit fonts for different orthographies or writing systems are not intercompatible. (Unicode was created to resolve this problem.)
In general ICT is moving to use of Unicode fonts. Old 8-bit fonts are also known as "legacy fonts." There is at least one project that has been assisting translation of material in legacy fonts into Unicode - RIFAL - and there is software to facilitate some conversions or recoding of fonts.
SIL, which offers both Unicode fonts and its old legacy 8-bit fonts for backward compatibility, makes this note about the two: "Unicode solutions are encouraged and are being developed for fonts and keyboards. Also available for some legacy systems are mapping files to convert data encoded in a legacy font to Unicode."
Wikipedia, "8-bit," http://en.wikipedia.org/wiki/8-bit
______, "Extended ASCII," http://en.wikipedia.org/wiki/Extended_ASCII