SITS - Revision history

Jnc: Add some links; avoid redirs

2025-04-14T17:44:15Z

Add some links; avoid redirs

← Older revision		Revision as of 17:44, 14 April 2025
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	}}		}}

	'''SITS''' means "Small Incompatible Timesharing System". It was a [[time-sharing]] [[operating system]] for a [[PDP-11/45]], created in the mid-1970s at [[MIT]] for running [[Logo]].		'''SITS''' means "Small Incompatible Timesharing System". It was a [[time-sharing]] [[operating system]] for a [[PDP-11/45]], created in the mid-1970s at [[Massachusetts Institute of Technology\|MIT]] for running [[Logo]].

	[[Image:SITS_and_logo.png\|thumb\|right\|SITS and Logo]]		[[Image:SITS_and_logo.png\|thumb\|right\|SITS and Logo]]
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	=== Overview ===		=== Overview ===

	SITS' design is vaguely reminiscent of [[Incompatible Timesharing System\|ITS]], with large influences from MIT's [[PDP-1-X Time Sharing System]]. Like ITS, there is a [[main memory]]-resident [[kernel]] [[debug]]ger; SALV for managing [[disk]]s; a [[TECO]]-like editor called TINTE for text editing, and [[DDT]] for debugging and running user programs. [[Process]]es can be [[PCLSRing\|PCLSR]]'ed just like in ITS. From the PDP-1-X it inherited capability-based security and the concept of spheres. It has a hierarchical tree-structured file system inspired by [[Multics]]. SITS supported [[raster]] [[display]]s similar to those used with the MIT-AI Knight TV, a few [[vector graphics\|vector]] displays, and [[General Turtle]] [[Turtle Terminal 2500\|2500 terminals]]. Programs can be stored in either [[PDP-11 Absolute Loader\|absolute loader]] format, or [[SITS PDUMP format\|pure dump]] format.		SITS' design is vaguely reminiscent of [[Incompatible Timesharing System\|ITS]], with large influences from MIT's [[PDP-1-X Time Sharing System]]. Like ITS, there is a [[main memory]]-resident [[kernel]] [[debug]]ger; SALV for managing [[disk]]s; a [[TECO]]-like editor called TINTE for text editing, and [[DDT]] for debugging and running user programs. [[Process]]es can be [[PCLSRing\|PCLSR]]'ed just like in ITS. From the PDP-1-X it inherited capability-based security and the concept of spheres. It has a hierarchical tree-structured [[file system]] inspired by [[Multics]]. SITS supported [[raster]] [[display]]s similar to those used with the MIT-AI [[Knight TV system]], a few [[vector graphics\|vector]] displays, and [[General Turtle]] [[Turtle Terminal 2500\|2500 terminals]]. Programs can be stored in either [[PDP-11 Absolute Loader\|absolute loader]] format, or [[SITS PDUMP format\|pure dump]] format.

	The kernel debugger was written by Radia Perlman and was called RUG from the phrase "snug as a bug in a rug". In addition to debugging, it can also read and write [[file]]s in the SITS [[file system]] which is how SITS is booted. It can also read files from paper ~~tapes~~, or from ITS through the Rubin 10-11 ~~shared memory~~ interface. The default file name is DAZZEL, perhaps a nod to the [[Dazzle Dart]] game that was hosted on the same machine.		The kernel debugger was written by Radia Perlman and was called RUG from the phrase "snug as a bug in a rug". In addition to debugging, it can also read and write [[file]]s in the SITS file system, which is how SITS is booted. It can also read files from [[paper tape]]s, or from ITS through the [[shared memory]] [[Rubin 10-11 interface]]. The default file name is DAZZEL, perhaps a nod to the [[Dazzle Dart]] game that was hosted on the same machine.

	AI memo 356 "Logo Progress Report 1973-1975" has this:		AI memo 356 "Logo Progress Report 1973-1975" has this:

Larsbrinkhoff: /* Overview */ Hardware problem caused flakiness.

2024-03-15T20:43:25Z

Overview: Hardware problem caused flakiness.

← Older revision		Revision as of 20:43, 15 March 2024
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	When the SITS PDP-11/45 was decommissioned from the Logo group, it was donated to what became the Concourse Computer Center. It did not continue running SITS due to instability problems. Instead the computer ran [[Unix Seventh Edition\|UNIX V7]], later 2[[BSD]], and was placed on the [[Chaosnet]].		When the SITS PDP-11/45 was decommissioned from the Logo group, it was donated to what became the Concourse Computer Center. It did not continue running SITS due to instability problems. Instead the computer ran [[Unix Seventh Edition\|UNIX V7]], later 2[[BSD]], and was placed on the [[Chaosnet]].

			Possibly, SITS reputation for being unstable was unwarranted, and partly due to a hardware problem. From one of the then-undergrads at CCC:

			<blockquote>
			So the biggest player at CCC was Gill Pratt, who is a bigwhig with Toyota's Robotics group now. I have said, "If a rainy day was a Unibus device, Gill could fix it." We DID get the Logo 11/45, but never ran SITS on it. But we know WHY SITS was so flaky. Eventually Gill found the root cause: A mis-wired FCO that left the high bit of the Floating Point Processor floating. Depending on the incident radio frequency interference, that line might go high and cause an illegal instruction trap, even if there was NO floating point instruction in progress!
			</blockquote>

	=== Little SITS ===		=== Little SITS ===

Larsbrinkhoff: /* Hardware support */ Link to frame buffer.

2024-02-27T06:50:31Z

Hardware support: Link to frame buffer.

← Older revision		Revision as of 06:50, 27 February 2024
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	\|-		\|-
	\|		\|
	\| Frame buffer		\| [[Frame buffer]]
	\| 660000-757777		\| 660000-757777
	\|		\|

Larsbrinkhoff: TINTE is not TECO either.

2023-09-08T05:57:55Z

TINTE is not TECO either.

← Older revision		Revision as of 05:57, 8 September 2023
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	=== Overview ===		=== Overview ===

	SITS' design is vaguely reminiscent of [[Incompatible Timesharing System\|ITS]], with large influences from MIT's [[PDP-1-X Time Sharing System]]. Like ITS, there is a [[main memory]]-resident [[kernel]] [[debug]]ger; SALV for managing [[disk]]s; [[TECO]] for text editing, and [[DDT]] for debugging and running user programs. [[Process]]es can be [[PCLSRing\|PCLSR]]'ed just like in ITS. From the PDP-1-X it inherited capability-based security and the concept of spheres. It has a hierarchical tree-structured file system inspired by [[Multics]]. SITS supported [[raster]] [[display]]s similar to those used with the MIT-AI Knight TV, a few [[vector graphics\|vector]] displays, and [[General Turtle]] [[Turtle Terminal 2500\|2500 terminals]]. Programs can be stored in either [[PDP-11 Absolute Loader\|absolute loader]] format, or [[SITS PDUMP format\|pure dump]] format.		SITS' design is vaguely reminiscent of [[Incompatible Timesharing System\|ITS]], with large influences from MIT's [[PDP-1-X Time Sharing System]]. Like ITS, there is a [[main memory]]-resident [[kernel]] [[debug]]ger; SALV for managing [[disk]]s; a [[TECO]]-like editor called TINTE for text editing, and [[DDT]] for debugging and running user programs. [[Process]]es can be [[PCLSRing\|PCLSR]]'ed just like in ITS. From the PDP-1-X it inherited capability-based security and the concept of spheres. It has a hierarchical tree-structured file system inspired by [[Multics]]. SITS supported [[raster]] [[display]]s similar to those used with the MIT-AI Knight TV, a few [[vector graphics\|vector]] displays, and [[General Turtle]] [[Turtle Terminal 2500\|2500 terminals]]. Programs can be stored in either [[PDP-11 Absolute Loader\|absolute loader]] format, or [[SITS PDUMP format\|pure dump]] format.

	The kernel debugger was written by Radia Perlman and was called RUG from the phrase "snug as a bug in a rug". In addition to debugging, it can also read and write [[file]]s in the SITS [[file system]] which is how SITS is booted. It can also read files from paper tapes, or from ITS through the Rubin 10-11 shared memory interface. The default file name is DAZZEL, perhaps a nod to the [[Dazzle Dart]] game that was hosted on the same machine.		The kernel debugger was written by Radia Perlman and was called RUG from the phrase "snug as a bug in a rug". In addition to debugging, it can also read and write [[file]]s in the SITS [[file system]] which is how SITS is booted. It can also read files from paper tapes, or from ITS through the Rubin 10-11 shared memory interface. The default file name is DAZZEL, perhaps a nod to the [[Dazzle Dart]] game that was hosted on the same machine.

Larsbrinkhoff: /* See also */ Link to tutorial.

2022-10-28T13:13:51Z

Larsbrinkhoff: /* See also */ PDUMP format and file system.

2022-10-28T10:14:15Z

Larsbrinkhoff: /* Hardware support */ No EAE.

2022-10-27T17:12:48Z

Hardware support: No EAE.

← Older revision		Revision as of 17:12, 27 October 2022
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	\|-		\|-
	\| [[KB11-A CPU]]		\| [[KB11-A CPU]]
	\| [[Central Processing Unit\|CPU~~]] with [[Extended Arithmetic Element\|EAE~~]]		\| [[Central Processing Unit\|CPU]]
	\|		\|
	\|		\|

Larsbrinkhoff: /* Preservation status */ Disk images work under emulator; it's SITS 122.

2022-10-19T11:51:52Z

Preservation status: Disk images work under emulator; it's SITS 122.

← Older revision		Revision as of 11:51, 19 October 2022
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	* SITS 134 from 1978.		* SITS 134 from 1978.
	* SITS 136 from 1979.		* SITS 136 from 1979.
	* A set of disk images from May 1978 with ~~an unknown~~ SITS ~~version~~.		* A set of disk images from May 1978 with SITS 122.

	Unsorted files from SITS, PDP-10 Logo, and PDP-11 Logo can be found here, courtesy of Ron Lebel: https://github.com/larsbrinkhoff/mit-logo-and-sits-raw-files		Unsorted files from SITS, PDP-10 Logo, and PDP-11 Logo can be found here, courtesy of Ron Lebel: https://github.com/larsbrinkhoff/mit-logo-and-sits-raw-files

Larsbrinkhoff: Info box and screen shot.

2022-10-19T11:08:44Z

Info box and screen shot.

← Older revision		Revision as of 11:08, 19 October 2022
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			{{Infobox OS
			\| name = SITS
			\| creator = [[MIT AI Lab]], Logo group
			\| current version = 136
			\| year introduced = 1974
			\| type = Multi-tasking, multi-user, virtual memory
			\| architecture = [[PDP-11]]
			}}

	'''SITS''' means "Small Incompatible Timesharing System". It was a [[time-sharing]] [[operating system]] for a [[PDP-11/45]], created in the mid-1970s at [[MIT]] for running [[Logo]].		'''SITS''' means "Small Incompatible Timesharing System". It was a [[time-sharing]] [[operating system]] for a [[PDP-11/45]], created in the mid-1970s at [[MIT]] for running [[Logo]].

			[[Image:SITS_and_logo.png\|thumb\|right\|SITS and Logo]]

	=== Overview ===		=== Overview ===

Larsbrinkhoff: /* Hardware support */ List of terminals.

2022-10-17T09:53:16Z

Hardware support: List of terminals.

@@ Line 130: / Line 130: @@
 | 770000-770017
 | 364
 |}

← Older revision		Revision as of 13:13, 28 October 2022
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	==See also==		==See also==

			* [[SITS tutorial]]
	* [[Installing SITS on SIMH]]		* [[Installing SITS on SIMH]]
	* [[List of SITS system calls]]		* [[List of SITS system calls]]

← Older revision		Revision as of 10:14, 28 October 2022
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	* [[Installing SITS on SIMH]]		* [[Installing SITS on SIMH]]
	* [[List of SITS system calls]]		* [[List of SITS system calls]]
			* [[SITS PDUMP format]]
			* [[SITS file system]]

	[[Category: PDP-11 Operating Systems]]		[[Category: PDP-11 Operating Systems]]
	[[Category: Non-DEC Operating Systems]]		[[Category: Non-DEC Operating Systems]]