MOS Technology 6509
Encyclopedia
The MOS Technology 6509, an enhanced version of the popular 6502
microprocessor
, was capable of addressing up to 1 megabyte
of RAM
via bank switching
. While numerous 6502-based processors could do bank switching, they did this via separate logic. The 6509 had this logic on-chip
.
The 6509 had a reputation for being difficult to program, due to its bank switching scheme, and never fared well. It was used in the ill-fated Commodore CBM-II
line of computers.
MOS Technology 6502
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
, was capable of addressing up to 1 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
of RAM
Random-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
via bank switching
Bank switching
Bank switching is a technique to increase the amount of usable memory beyond the amount directly addressable by the processor. It can be used to configure a system differently at different times; for example, a ROM required to start a system from diskette could be switched out when no longer...
. While numerous 6502-based processors could do bank switching, they did this via separate logic. The 6509 had this logic on-chip
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
.
The 6509 had a reputation for being difficult to program, due to its bank switching scheme, and never fared well. It was used in the ill-fated Commodore CBM-II
Commodore CBM-II
The Commodore CBM-II series was a short-lived range of 8-bit personal computers from Commodore Business Machines , intended as a follow-on to the Commodore PET series, released in 1982.-Technical description:...
line of computers.