Channel - Revision history

Jnc: rm duplicate content (now in 'IBM I/O channel')

2024-04-09T15:18:35Z

rm duplicate content (now in 'IBM I/O channel')

Jnc: /* See also */ +IBM I/O channel

2024-04-09T12:37:41Z

‎See also: +IBM I/O channel

Jnc: +cat

2018-12-15T14:27:25Z

+cat

Jnc: mention connections

2018-11-08T13:54:07Z

mention connections

Jnc: Add control words/program

2018-11-08T13:42:12Z

Add control words/program

Jnc: +See also

2018-11-07T18:50:57Z

+See also

Jnc: typo

2018-11-07T18:38:50Z

typo

Jnc: Mention cond branch

2018-11-07T18:38:27Z

Mention cond branch

Jnc: A pretty good start

2018-11-07T14:18:32Z

A pretty good start

New page

A '''channel''' is a block of [[hardware]] (effectively a [[co-processor]]) which performs [[input/output|I/O]] operations, off-loading that work from the main [[Central Processing Unit|CPU]]; they usually have direct access to [[main memory]].

They are most commonly found on [[mainframe]] systems; on smaller machines, mechanisms such as [[Direct Memory Access|DMA]] from [[device controller]]s do a lot of what a channel does.

The details vary considerably from manufacturer to manufacturer: for instance, the Peripheral Processing Units of the [[CDC 6600]] are effectively channels, but they are essentially complete [[minicomputer]]s (although they are implemented with shared hardware). The channels of [[International Business Machines|IBM]] mainframes are programmable, but are much more limited in functionality; they are [[finite state machine]]s.

IBM channels come in two varieties: a 'multiplexer channel' handles a group of slow-speed devices, and interleaves operations to each of them, with each transfer handling single small data item (e.g. a [[byte]]); a 'selector channel' handles high-speed devices such as [[disk]]s and [[magnetic tape drive]]s, and transfers an entire block at a time.

They were apparently first introduced with the [[IBM 709]], and other manufacturers copied the idea.

{{semi-stub}}

@@ Line 3: / Line 3: @@
 They are most commonly found on [[mainframe]] systems; on smaller machines, mechanisms such as [[Direct Memory Access|DMA]] from [[device controller]]s do a lot of what a channel does.
-The details vary considerably from manufacturer to manufacturer: for instance, the Peripheral Processing Units of the [[CDC 6600]] are effectively channels, but they are essentially complete [[minicomputer]]s (although they are implemented with shared hardware).
+The details vary considerably from manufacturer to manufacturer: for instance, the Peripheral Processing Units of the [[CDC 6600]] are effectively channels, but they are essentially complete [[minicomputer]]s (although the individual PPU's are implemented with one set of shared hardware). The channels of [[International Business Machines|IBM]] mainframes are programmable, but are much more limited in functionality; they are [[finite state machine]]s, with [[conditional branch]]ing capability.
 For the channels which include a specialized control unit, not a full general-purpose CPU, the individual operations are called '''channel command words'''; they are generally stored in main memory, and are organized into '''channel programs'''.
 Channels were apparently first introduced with the [[IBM 709]], and other manufacturers copied the idea.

@@ Line 12: / Line 12: @@
 Channels were apparently first introduced with the [[IBM 709]], and other manufacturers copied the idea.
 ==See also==
 * [[DF10 Data Channel]]
 [[Category: Hardware Basics]]

← Older revision		Revision as of 14:27, 15 December 2018
Line 18:		Line 18:

	{{semi-stub}}		{{semi-stub}}
		+
		+	[[Category: Hardware Basics]]

@@ Line 1: / Line 1: @@
-A '''channel''' is a block of [[hardware]] (effectively a [[co-processor]]) which performs [[input/output|I/O]] operations, off-loading that work from the main [[Central Processing Unit|CPU]]; they usually have direct access to [[main memory]].
+A '''channel''' is a block of [[hardware]] (effectively a [[co-processor]]) which performs [[input/output|I/O]] operations, off-loading that work from the main [[Central Processing Unit|CPU]]; they are connected to [[peripheral]]s, and usually have direct access to [[main memory]].
 They are most commonly found on [[mainframe]] systems; on smaller machines, mechanisms such as [[Direct Memory Access|DMA]] from [[device controller]]s do a lot of what a channel does.
@@ Line 7: / Line 7: @@
 The channels of [[International Business Machines|IBM]] mainframes are programmable, but are much more limited in functionality; they are [[finite state machine]]s, with [[conditional branch]]ing capability.
-For the channels which include a specialized control unit, not a full general-purpose CPU, the individual operations are called '''channel command words'''; they are generally stored in main memory, and are organized into a '''channel program'''.
+For the channels which include a specialized control unit, not a full general-purpose CPU, the individual operations are called '''channel command words'''; they are generally stored in main memory, and are organized into '''channel programs'''.
 IBM channels come in two varieties: a '''multiplexer channel''' handles a group of slow-speed devices, and interleaves operations to each of them, with each transfer handling single small data item (e.g. a [[byte]]); a '''selector channel''' handles high-speed devices such as [[disk]]s and [[magnetic tape drive]]s, and transfers an entire block at a time.

@@ Line 3: / Line 3: @@
 They are most commonly found on [[mainframe]] systems; on smaller machines, mechanisms such as [[Direct Memory Access|DMA]] from [[device controller]]s do a lot of what a channel does.
-The details vary considerably from manufacturer to manufacturer: for instance, the Peripheral Processing Units of the [[CDC 6600]] are effectively channels, but they are essentially complete [[minicomputer]]s (although they are implemented with shared hardware). The channels of [[International Business Machines|IBM]] mainframes are programmable, but are much more limited in functionality; they are [[finite state machine]]s, with [[conditional branch]]ing capability.
+The details vary considerably from manufacturer to manufacturer: for instance, the Peripheral Processing Units of the [[CDC 6600]] are effectively channels, but they are essentially complete [[minicomputer]]s (although they are implemented with shared hardware).
-IBM channels come in two varieties: a 'multiplexer channel' handles a group of slow-speed devices, and interleaves operations to each of them, with each transfer handling single small data item (e.g. a [[byte]]); a 'selector channel' handles high-speed devices such as [[disk]]s and [[magnetic tape drive]]s, and transfers an entire block at a time.
+The channels of [[International Business Machines|IBM]] mainframes are programmable, but are much more limited in functionality; they are [[finite state machine]]s, with [[conditional branch]]ing capability.
 Channels were apparently first introduced with the [[IBM 709]], and other manufacturers copied the idea.
 ==See also==
 * [[DF10 Data Channel]]
 {{semi-stub}}

← Older revision		Revision as of 18:50, 7 November 2018
Line 8:		Line 8:

	Channels were apparently first introduced with the [[IBM 709]], and other manufacturers copied the idea.		Channels were apparently first introduced with the [[IBM 709]], and other manufacturers copied the idea.
		+
		+	==See also==
		+	* [[DF10 Data Channel]]

	{{semi-stub}}		{{semi-stub}}