Programmed I/O - Revision history

Jnc: +See also - Direct Memory Access

2021-10-20T21:12:07Z

+See also - Direct Memory Access

Jnc: +cat

2018-12-16T00:06:49Z

+cat

Jnc: Avoid redir

2017-09-21T19:47:36Z

Avoid redir

Jnc: Tweak def

2017-06-04T17:23:28Z

Tweak def

Jnc: A decentr start

2017-06-04T02:53:53Z

A decentr start

New page

'''Programmed I/O''' refers to a style of I/O which is performed by code running in the [[CPU]] - as opposed to [[Direct Memory Access]], in which the device communicates directly with [[main memory]].

There are two main types of Programmed I/O: i) '''polled''', in which the CPU has to regularly check the device to see if it needs a data transfer, and ii) '''interrupt-driven''', where the device causes an [[interrupt]] in the CPU when it needs to be serviced.

The former can have a fairly high level of overhead (the device must be constantly checked, whether it has anything to do or not), and puts limits on the structure of the program. The latter can produce high levels of overhead when the device is running (due to the overhead involved in saving and restoring the context when an interrupt happens); as such, it is not well-suited to high-speed devices such as s[[disk]]s, which typically use DMA.

@@ Line 1: / Line 1: @@
-'''Programmed I/O''' refers to a style of I/O in which the transfer of data is performed by code running in the [[Central Processing Unit|CPU]], using instructions performed by the CPU to move data - as opposed to [[Direct Memory Access]], in which the device communicates directly with [[main memory]].
+'''Programmed I/O''' refers to a style of I/O in which the transfer of data is performed by code running in the [[Central Processing Unit|CPU]], using [[instruction]]s performed by the CPU to move data - as opposed to [[Direct Memory Access|DMA]], in which the [[peripheral|device]] communicates directly with [[main memory]].
 There are two main types of Programmed I/O: i) '''polled''', in which the CPU has to regularly check the device to see if it needs a data transfer, and ii) '''interrupt-driven''', where the device causes an [[interrupt]] in the CPU when it needs to be serviced.
 The former can have a fairly high level of overhead (the device must be constantly checked, whether it has anything to do or not), and also puts limits on the structure of the program. The latter can produce high levels of overhead when the device is running at high speed (due to the overhead involved in saving and restoring the context when an interrupt happens); as such, it is not well-suited to high-speed devices such as [[disk]]s, which typically use DMA.
 [[Category: Computer Basics]]

← Older revision		Revision as of 00:06, 16 December 2018
Line 4:		Line 4:

	The former can have a fairly high level of overhead (the device must be constantly checked, whether it has anything to do or not), and also puts limits on the structure of the program. The latter can produce high levels of overhead when the device is running at high speed (due to the overhead involved in saving and restoring the context when an interrupt happens); as such, it is not well-suited to high-speed devices such as [[disk]]s, which typically use DMA.		The former can have a fairly high level of overhead (the device must be constantly checked, whether it has anything to do or not), and also puts limits on the structure of the program. The latter can produce high levels of overhead when the device is running at high speed (due to the overhead involved in saving and restoring the context when an interrupt happens); as such, it is not well-suited to high-speed devices such as [[disk]]s, which typically use DMA.
		+
		+	[[Category: Computer Basics]]

@@ Line 1: / Line 1: @@
-'''Programmed I/O''' refers to a style of I/O which is performed by code running in the [[CPU]], using instructions performed by the CPU to move data - as opposed to [[Direct Memory Access]], in which the device communicates directly with [[main memory]].
+'''Programmed I/O''' refers to a style of I/O in which the transfer of data is performed by code running in the [[Central Processing Unit|CPU]], using instructions performed by the CPU to move data - as opposed to [[Direct Memory Access]], in which the device communicates directly with [[main memory]].
 There are two main types of Programmed I/O: i) '''polled''', in which the CPU has to regularly check the device to see if it needs a data transfer, and ii) '''interrupt-driven''', where the device causes an [[interrupt]] in the CPU when it needs to be serviced.
 The former can have a fairly high level of overhead (the device must be constantly checked, whether it has anything to do or not), and also puts limits on the structure of the program. The latter can produce high levels of overhead when the device is running at high speed (due to the overhead involved in saving and restoring the context when an interrupt happens); as such, it is not well-suited to high-speed devices such as [[disk]]s, which typically use DMA.