MOS Technology 6509: Meaning (information, definition, explanation, facts)

The MOS Technology 6509 was an enhanced version of the popular 6502 microprocessor, capable of addressing up to 1 megabyte of RAM via bank switching. While numerous computers based on the 6502 series did bank switching, they did this via separate logic. The 6509 had this logic on board.

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.