Interface Message Processor - Revision history

Jnc: /* External links */ Link AFIPS

2025-10-06T10:15:49Z

‎External links: Link AFIPS

Jnc: Move Pluribus IMP image here

2025-09-29T13:33:33Z

Move Pluribus IMP image here

Jnc: Link to Series 16 page

2025-09-29T11:13:13Z

Link to Series 16 page

Jnc: /* External links */ + "'deep dive' analysis of [some of] the IMP code from the early 1970s"

2025-09-13T15:34:03Z

‎External links: + "'deep dive' analysis of [some of] the IMP code from the early 1970s"

Jnc: /* External links */ +The IMP Lights story

2025-09-07T16:30:41Z

‎External links: +The IMP Lights story

Jnc: The DDP-516 came in non-ruggedized form too

2025-01-21T05:55:00Z

The DDP-516 came in non-ruggedized form too

Jnc: Add image of a 516 IMP

2025-01-15T12:55:51Z

Add image of a 516 IMP

Jnc: +links

2024-12-16T02:57:18Z

+links

Jnc: /* External links */ +Initial Design for Interface Message Processors for the ARPA Computer Network

2023-12-17T18:49:53Z

‎External links: +Initial Design for Interface Message Processors for the ARPA Computer Network

Jnc: /* External links */ +DMC manual

2021-11-16T01:44:48Z

‎External links: +DMC manual

@@ Line 17: / Line 17: @@
 * [http://www.bitsavers.org/pdf/bbn/imp/BBN1763_IMP_InitialDesign_Jan69.pdf Initial Design for Interface Message Processors for the ARPA Computer Network]
 * [http://walden-family.com/impcode/ Resurrection of the 1973 IMP code] - While focused on the retrieval, and running under a simulator, of the original IMP code, this site contains much other IMP-related material too (manuals, etc)
-** F.E. Heart, R.E. Kahn, S.M. Ornstein, W.R. Crowther, and D.C. Walden, [http://www.walden-family.com/public/1970-imp-afips.pdf The interface message processor for the ARPA computer network], Proceedings AFIPS, 1970 SJCC, Vol. 36, pp. 551-567.
+** F.E. Heart, R.E. Kahn, S.M. Ornstein, W.R. Crowther, and D.C. Walden, [http://www.walden-family.com/public/1970-imp-afips.pdf The interface message processor for the ARPA computer network], Proceedings [[American Federation of Information Processing Societies|AFIPS]], 1970 SJCC, Vol. 36, pp. 551-567.
 ** [https://walden-family.com/impcode/imp-hardware.pdf Intermodem Processor System] - Honeywell manual covering much of the custom IMP hardware
 **  [https://walden-family.com/impcode/imp-code.pdf The Arpanet IMP Program: Retrospective and Resurrection]

@@ Line 1: / Line 1: @@
-[[Image:516IMP.jpg|thumb|right|250px|Honeywell 516 IMP]]
+[[Image:516IMP.jpg|thumb|right|350px|Honeywell 516 IMP]]
 The '''Interface Message Processor''' (or '''IMP''', as they were universally known) was the [[packet switch]] which the [[ARPANET]] was made out of; the IMPs were connected to each other via high-speed dedicated point-point telephone links, connected to the IMPs via a [[modem]]. All ARPANET [[host]]s connected to an IMP; connection of a host to an IMP required a special [[network interface]], an [[IMP interface]], which used the asynchronous bit-serial [[1822 interface]] standard, which was especially created for the ARPANET.
 A message from one Host to another was sent via the source Host's IMP, then routed through some number (possibly zero) intermediate IMPs, then through the destination Host's IMP (possibly the same IMP as the first one, in which case the message never went over a telephone line), on to the destination Host. The [[protocol]] which controlled both the channel between the host and IMP, and inter-host communication, was the [[Host-to-IMP Protocol]].
 The IMPs were 'ruggedized' [[Honeywell]] [[Series 16|DDP-516]] [[minicomputer]]s, with added special high-speed modem interfaces, and 1822 host interfaces. Later, other variant minicomputers were also used; the Honeywell [[Series 16|DDP-316]] (a slower, and presumably cost-reduced, [[program compatible]] version of the 516), the [[Pluribus]], and the [[Bolt, Beranek, and Newman|BBN]] C/30 (which first had [[microcode]] which emulated the Honeywell machines; later an updated "native mode" microcode exposing the full 20-bit hardware).
 {{semi-stub}}
 ==External links==

@@ Line 5: / Line 5: @@
 A message from one Host to another was sent via the source Host's IMP, then routed through some number (possibly zero) intermediate IMPs, then through the destination Host's IMP (possibly the same IMP as the first one, in which case the message never went over a telephone line), on to the destination Host. The [[protocol]] which controlled both the channel between the host and IMP, and inter-host communication, was the [[Host-to-IMP Protocol]].
-The IMPs were 'ruggedized' [[Honeywell]] DDP-516 [[minicomputer]]s, with added special high-speed modem interfaces, and 1822 host interfaces. Later, other variant minicomputers were also used; the Honeywell DDP-316 (a slower, and presumably cost-reduced, [[program compatible]] version of the 516), the [[Pluribus]], and the [[Bolt, Beranek, and Newman|BBN]] C/30 (which first had [[microcode]] which emulated the Honeywell machines; later an updated "native mode" microcode exposing the full 20-bit hardware).
+The IMPs were 'ruggedized' [[Honeywell]] [[Series 16|DDP-516]] [[minicomputer]]s, with added special high-speed modem interfaces, and 1822 host interfaces. Later, other variant minicomputers were also used; the Honeywell [[Series 16|DDP-316]] (a slower, and presumably cost-reduced, [[program compatible]] version of the 516), the [[Pluribus]], and the [[Bolt, Beranek, and Newman|BBN]] C/30 (which first had [[microcode]] which emulated the Honeywell machines; later an updated "native mode" microcode exposing the full 20-bit hardware).
 {{semi-stub}}

@@ Line 20: / Line 20: @@
 ** [http://bitsavers.org/pdf/computerControlCompany/series16/h316/70130072180L_DMC_Option_Jun75.pdf H316-20 Data Multiplex Control Option] - DMA controller heavily used by the IMP modem and host interface hardware
 * [http://www.chiappa.net/~jnc/tech/arpanet.html ARPANET Technical Information]
 * [https://elists.isoc.org/pipermail/internet-history/2025-August/010815.html The IMP Lights story] - improving the reliability of the IMPs
 [[Category: ARPANET]]

@@ Line 20: / Line 20: @@
 ** [http://bitsavers.org/pdf/computerControlCompany/series16/h316/70130072180L_DMC_Option_Jun75.pdf H316-20 Data Multiplex Control Option] - DMA controller heavily used by the IMP modem and host interface hardware
 * [http://www.chiappa.net/~jnc/tech/arpanet.html ARPANET Technical Information]
 [[Category: ARPANET]]

← Older revision		Revision as of 12:55, 15 January 2025
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		+	[[Image:516IMP.jpg\|thumb\|right\|250px\|Honeywell 516 IMP]]
		+
	The '''Interface Message Processor''' (or '''IMP''', as they were universally known) was the [[packet switch]] which the [[ARPANET]] was made out of; the IMPs were connected to each other via high-speed dedicated point-point telephone links, connected to the IMPs via a [[modem]]. All ARPANET [[host]]s connected to an IMP; connection of a host to an IMP required a special [[network interface]], an [[IMP interface]], which used the asynchronous bit-serial [[1822 interface]] standard, which was especially created for the ARPANET.		The '''Interface Message Processor''' (or '''IMP''', as they were universally known) was the [[packet switch]] which the [[ARPANET]] was made out of; the IMPs were connected to each other via high-speed dedicated point-point telephone links, connected to the IMPs via a [[modem]]. All ARPANET [[host]]s connected to an IMP; connection of a host to an IMP required a special [[network interface]], an [[IMP interface]], which used the asynchronous bit-serial [[1822 interface]] standard, which was especially created for the ARPANET.

@@ Line 3: / Line 3: @@
 A message from one Host to another was sent via the source Host's IMP, then routed through some number (possibly zero) intermediate IMPs, then through the destination Host's IMP (possibly the same IMP as the first one, in which case the message never went over a telephone line), on to the destination Host. The [[protocol]] which controlled both the channel between the host and IMP, and inter-host communication, was the [[Host-to-IMP Protocol]].
-The IMPs were Honeywell DDP-516 'ruggedized' [[minicomputer]]s, with added special high-speed modem interfaces, and 1822 host interfaces. Later, other variant minicomputers were also used; the Honeywell DDP-316 (the non-ruggedized version of the 516), the Pluribus, and the [[BBN]] C/30 (which first had [[microcode]] which emulated the Honeywell machines, later an updated "native mode" microcode exposing the full 20-bit hardware).
+The IMPs were [[Honeywell]] DDP-516 'ruggedized' [[minicomputer]]s, with added special high-speed modem interfaces, and 1822 host interfaces. Later, other variant minicomputers were also used; the Honeywell DDP-316 (the non-ruggedized version of the 516), the [[Pluribus]], and the [[BBN]] C/30 (which first had [[microcode]] which emulated the Honeywell machines; later an updated "native mode" microcode exposing the full 20-bit hardware).
 {{semi-stub}}