Editing Bank switching (section)

{{Short description|A technique to increase the amount of usable memory}}
{{Confuse|Paging}}
{{Use dmy dates|date=February 2020|cs1-dates=y}}
[[File:Bankswitch memory map.svg|thumb|right|A hypothetical [[memory map]] of bank-switched memory for a processor that can only address 64&nbsp;KB. This scheme shows 200&nbsp;KB of memory, of which only 64&nbsp;KB can be accessed at any time by the processor. The operating system must manage the bank-switching operation to ensure that program execution can continue when part of memory is not accessible to the processor.]]

'''Bank switching''' is a technique used in computer design to increase the amount of usable memory beyond the amount directly addressable by the [[Processor (computing)|processor]]<ref name="Aspinall_1978"/> instructions. It can be used to configure a system differently at different times; for example, a [[read-only memory|ROM]] required to [[booting|start a system]] from diskette could be switched out when no longer needed. In video game systems, bank switching allowed larger games to be developed for play on existing consoles.

Bank switching originated in [[minicomputer]] systems.<ref name="Bell_1971"/> Many modern [[microcontroller]]s and [[microprocessor]]s use bank switching to manage [[random-access memory]], non-volatile memory, input-output devices and system management registers in small [[embedded system]]s. The technique was common in [[8-bit]] [[microcomputer]] systems. Bank-switching may also be used to work around limitations in address bus width, where some hardware constraint prevents straightforward addition of more address lines, and to work around limitations in the [[Instruction set architecture|ISA]], where the addresses generated are narrower than the address bus width. Some control-oriented microprocessors use a bank-switching technique to access internal I/O and control registers, which limits the number of register address bits that must be used in every instruction.

Unlike memory management by [[paging]], data is not exchanged with a mass storage device like [[disk storage]]. Data remains in quiescent storage in a memory area that is not currently accessible to the processor (although it may be accessible to the video display, [[Direct memory access|DMA controller]], or other subsystems of the computer) without the use of special prefix instructions.