Difference between revisions of "SITS"
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| − | '''SITS''' means "Small | + | '''SITS''' means "Small Incompatible Timesharing System". It was a [[time-sharing]] [[operating system]] for the [[PDP-11]], created in the mid-1970s at [[MIT]] for running [[Logo]]. |
| − | Its design is vaguely reminiscent of ITS. Like ITS, there is a | + | Its design is vaguely reminiscent of [[Incompatible Timesharing System|ITS]]. 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 [[PCLSR]]'ed just like in ITS. |
| − | 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 | + | 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. 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: | ||
| Line 10: | Line 10: | ||
Originally Logo was implemented in [[assembly language]] on the PDP-10. In order to provide a computer system dedicated to educational use, it was adapted for the PDP-11. The first milestone in this direction was the completion in 1973-1974 of a dedicated timesharing system running 11LOGO. | Originally Logo was implemented in [[assembly language]] on the PDP-10. In order to provide a computer system dedicated to educational use, it was adapted for the PDP-11. The first milestone in this direction was the completion in 1973-1974 of a dedicated timesharing system running 11LOGO. | ||
| − | The was not an entirely satisfactory solution because of the inability of the system to be self-maintaining or to run other languages or special purpose jobs (like a [[simulation]] environment or an educational real-time game). During 1974-1975, our programming staff, under the direction or R. Lebel, completed the design and implementation of a general purpose multi-language timesharing system for the [[PDP-11/45]]. The SITS timesharing system was developed to provide an environment suitable for running Logo and other PDP-11/45 programs. It incorporates a [[Multics]]-like tree structured | + | The was not an entirely satisfactory solution because of the inability of the system to be self-maintaining or to run other languages or special purpose jobs (like a [[simulation]] environment or an educational real-time game). During 1974-1975, our programming staff, under the direction or R. Lebel, completed the design and implementation of a general purpose multi-language timesharing system for the [[PDP-11/45]]. The SITS timesharing system was developed to provide an environment suitable for running Logo and other PDP-11/45 programs. It incorporates a [[Multics]]-like tree structured file system including (potentially) full access control. It also provides unique capabilities for running programs as multiple process systems, rather than the more common single process approach, and the ability for each user to run many [[job]]s simultaneously. The system include provisions for using both the older refreshed [[display]]s and our new [[raster]] displays. |
</blockquote> | </blockquote> | ||
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Only a few snapshots of SITS exist on ITS backup tapes from the [[MIT Artificial Intelligence Laboratory|AI Lab]] [[PDP-10]]. | Only a few snapshots of SITS exist on ITS backup tapes from the [[MIT Artificial Intelligence Laboratory|AI Lab]] [[PDP-10]]. | ||
| − | * SITS version 1146 from October 1975 | + | * SITS version 1146 from October 1975; |
| + | * NSITS versions 111, 112 from December 1975; | ||
* A set of disk images from May 1978 with an unknown SITS version. | * A set of disk images from May 1978 with an unknown SITS version. | ||
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This is the list of supported, or actually required hardware for SITS version 1146: | This is the list of supported, or actually required hardware for SITS version 1146: | ||
| − | * KB11-A CPU with | + | * [[KB11-A CPU]] with [[KT11-C Memory Management Unit]] |
| − | * 128K core memory | + | * 128K [[core]] memory |
| − | * EAE | + | * EAE [[PDP-11 Extended Instruction Set]] |
| − | * FP11 | + | <!-- ??? In the -11/45, the EAE is part of the basic CPU --> |
| − | * | + | * [[FP11-B Floating-Point Processor]] |
| − | * PC11 paper tape reader/punch | + | * KW11-P programmable clock |
| − | * DC11 | + | * [[PC11 High-Speed Paper-Tape Reader/Punch Control|PC11]] [[paper tape]] reader/punch |
| − | * DH11 | + | * [[DC11 asynchronous serial line interface]] |
| − | * RF11 fixed head disk | + | * [[DH11 asynchronous serial line interface]] |
| − | * RK11 moving head disk | + | * [[RF11 disk controller|RF11]] [[fixed-head disk]] |
| + | * [[RK11 disk controller|RK11]] moving head disk | ||
* Tom Knight's NG vector display controller | * Tom Knight's NG vector display controller | ||
* Ron Lebel's TV raster display controller | * Ron Lebel's TV raster display controller | ||
Revision as of 13:20, 28 September 2019
SITS means "Small Incompatible Timesharing System". It was a time-sharing operating system for the PDP-11, created in the mid-1970s at MIT for running Logo.
Its design is vaguely reminiscent of ITS. Like ITS, there is a main memory-resident kernel debugger; SALV for managing disks; TECO for text editing, and DDT for debugging and running user programs. Processes can be PCLSR'ed just like in ITS.
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 files in the SITS file system which is how SITS is booted. 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:
Originally Logo was implemented in assembly language on the PDP-10. In order to provide a computer system dedicated to educational use, it was adapted for the PDP-11. The first milestone in this direction was the completion in 1973-1974 of a dedicated timesharing system running 11LOGO.
The was not an entirely satisfactory solution because of the inability of the system to be self-maintaining or to run other languages or special purpose jobs (like a simulation environment or an educational real-time game). During 1974-1975, our programming staff, under the direction or R. Lebel, completed the design and implementation of a general purpose multi-language timesharing system for the PDP-11/45. The SITS timesharing system was developed to provide an environment suitable for running Logo and other PDP-11/45 programs. It incorporates a Multics-like tree structured file system including (potentially) full access control. It also provides unique capabilities for running programs as multiple process systems, rather than the more common single process approach, and the ability for each user to run many jobs simultaneously. The system include provisions for using both the older refreshed displays and our new raster displays.
Preservation status
Only a few snapshots of SITS exist on ITS backup tapes from the AI Lab PDP-10.
- SITS version 1146 from October 1975;
- NSITS versions 111, 112 from December 1975;
- A set of disk images from May 1978 with an unknown SITS version.
Hardware support
This is the list of supported, or actually required hardware for SITS version 1146:
- KB11-A CPU with KT11-C Memory Management Unit
- 128K core memory
- EAE PDP-11 Extended Instruction Set
- FP11-B Floating-Point Processor
- KW11-P programmable clock
- PC11 paper tape reader/punch
- DC11 asynchronous serial line interface
- DH11 asynchronous serial line interface
- RF11 fixed-head disk
- RK11 moving head disk
- Tom Knight's NG vector display controller
- Ron Lebel's TV raster display controller
- Lebel keyboards
