Front end - Revision history

Jnc: Avoid redir

2022-09-23T19:53:34Z

Avoid redir

Jnc: Not just I/O

2021-01-28T10:39:00Z

Not just I/O

Jnc: +cat

2018-12-15T14:28:34Z

+cat

Jnc: Proper cat

2018-10-18T19:54:43Z

Proper cat

Jnc: Copyedit, add more

2018-04-20T18:55:33Z

Copyedit, add more

Jnc: A start...

2018-04-20T15:06:09Z

A start...

New page

The term '''front end''' usually refers to a small computer attached to a large one, which is used to offload [[input/output]] work from the larger machine. (Hence the alternative terms '''I/O processor''' and '''peripheral processor''').

The advantage of offloading I/O activity to a separate computer is that the acivity involved in the overhead of processing an [[interrupt]] from a device (e.g. saving [[register]] contents) can be significant, so avoid bothering the main CPU with this work can produce significant efficiencies.

The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the [[main memory]] used by the main CPU, a technique used in the PPUs of the [[CDC 6600]], the [[DL10]] of the [[PDP-10]] family, etc.

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 There are several advantages to offloading I/O activity to a separate computer. First, the obvious one is the ability to bring additional processing power to bear. Second, large mainframes are typically optimized for doing large-scale computations, not doing I/O. Also, the overhead involved in processing an [[interrupt]] from a device (e.g. saving [[register]] contents) can be significant, particularly for small data items, so avoiding bothering the main CPU with this cost (often larger in a mainframe than in a smaller machine) can produce significant efficiencies.
-The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the [[main memory]] used by the main CPU, a technique used in the PPUs of the [[CDC 6600]], the [[DL10]]-[[PDP-11]] combination of the [[PDP-10]] family, etc.
+The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the [[main memory]] used by the main CPU, a technique used in the PPUs of the [[CDC 6600]], the [[DL10 PDP-11 Data Link|DL10]]-[[PDP-11]] combination of the [[PDP-10]] family, etc.
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 [[Category: Hardware Basics]]

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-The term '''front end''' usually refers to a small computer attached to a large one (usually a [[mainframe]]), which is used to offload [[input/output]] work from the larger machine. (Hence the alternative terms '''I/O processor''' and '''peripheral processor'''.)
+The term '''front end''' usually refers to a small computer attached to a large one (usually a [[mainframe]]). Initially, they were used to offload [[input/output]] work from the larger machine. (Hence the alternative terms '''I/O processor''' and '''peripheral processor'''.) Later, they came to be used to replace the complex (and expensive) [[front panel]]s of larger machines. In addition to display and control functions, they were usually capable of other functionality also: on [[microcode]]d machines with loadable microcode, they loaded that; they could also perform [[bootstrap]] and [[diagnostic]] functions.
-There are several advantages to offloading I/O activity to a separate computer. First, the obvious one is the ability to bring additional processing power to bear. Second, large mainframes are typically optimized for doing large-scale computations, not doing I/O. Also, the overhead involved in processing an [[interrupt]] from a device (e.g. saving [[register]] contents) can be significant, so avoiding bothering the main CPU with this (often larger in a mainframe than in a smaller machine) can produce significant efficiencies.
+There are several advantages to offloading I/O activity to a separate computer. First, the obvious one is the ability to bring additional processing power to bear. Second, large mainframes are typically optimized for doing large-scale computations, not doing I/O. Also, the overhead involved in processing an [[interrupt]] from a device (e.g. saving [[register]] contents) can be significant, particularly for small data items, so avoiding bothering the main CPU with this cost (often larger in a mainframe than in a smaller machine) can produce significant efficiencies.
 The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the [[main memory]] used by the main CPU, a technique used in the PPUs of the [[CDC 6600]], the [[DL10]]-[[PDP-11]] combination of the [[PDP-10]] family, etc.

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	The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the [[main memory]] used by the main CPU, a technique used in the PPUs of the [[CDC 6600]], the [[DL10]]-[[PDP-11]] combination of the [[PDP-10]] family, etc.		The front end machine can communicate with the main CPU in a number of ways. It may have direct access to the [[main memory]] used by the main CPU, a technique used in the PPUs of the [[CDC 6600]], the [[DL10]]-[[PDP-11]] combination of the [[PDP-10]] family, etc.

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