PDP-11/20 - Revision history

Jnc: /* Extensions */ Update Bell Labs URLs (blast Nokia)

2025-06-30T20:11:02Z

‎Extensions: Update Bell Labs URLs (blast Nokia)

Jnc: /* External links */ +pdp11/20 Price List

2024-10-11T21:22:38Z

‎External links: +pdp11/20 Price List

Jnc: /* External links */ +original documents

2023-12-31T17:27:48Z

‎External links: +original documents

Jnc: Fill out infobox

2023-12-31T16:17:41Z

Fill out infobox

Jnc: /* External links */ +http://hampage.hu/pdp-11/1120.html

2023-09-22T17:00:51Z

‎External links: +http://hampage.hu/pdp-11/1120.html

Jnc: /* See also */ +KS11 Memory Protection and Relocation option

2023-06-30T00:46:34Z

‎See also: +KS11 Memory Protection and Relocation option

Jnc: software, manuals, FMPS

2022-07-06T20:05:10Z

software, manuals, FMPS

Jnc: /* Extensions */ mention KS11

2022-07-06T19:47:20Z

‎Extensions: mention KS11

Jnc: /* External links */ +PDP-11/20 Processor Handbook

2022-04-05T23:16:04Z

‎External links: +PDP-11/20 Processor Handbook

Jnc: bah, typo

2020-05-20T11:17:39Z

bah, typo

@@ Line 38: / Line 38: @@
 One was a [[co-processor]] for the multiply/divide functions, the [[KE11-A Extended Arithmetic Element]]; rather than additional [[instruction]]s in the CPU, it was implemented as a [[peripheral|device]] on the [[bus]], making this model somewhat incompatible with the rest of the PDP-11's.
-The [[KS11 Memory Protection and Relocation option|KS11]] was apparently DEC's first attempt at an add-on to provide memory management to the -11/20. Other than a [https://www.bell-labs.com/usr/dmr/www/odd.html funny story], little is known of it. The extremely rare [[KT11-B Paging Option]] was logically an addition to the CPU, interposed between the KA11 and the UNIBUS (but also having a few ties into the CPU); it allowed [[hardware]]-based [[time-sharing]], and use of up to the full 248 KBytes of memory addressable by the UNIBUS.
+The [[KS11 Memory Protection and Relocation option|KS11]] was apparently DEC's first attempt at an add-on to provide memory management to the -11/20. Other than a [https://www.nokia.com/bell-labs/about/dennis-m-ritchie/odd.html funny story], little is known of it. The extremely rare [[KT11-B Paging Option]] was logically an addition to the CPU, interposed between the KA11 and the UNIBUS (but also having a few ties into the CPU); it also allowed [[hardware]]-based [[time-sharing]], and use of up to the full 248 KBytes of memory addressable by the UNIBUS.
 ==Software==

@@ Line 70: / Line 70: @@
 ==External links==
 * [http://www.bitsavers.org/pdf/dec/pdp11/1120/ 11/20] - documentation at [[Bitsavers]]
 ** [http://www.bitsavers.org/pdf/dec/pdp11/1120/1120_SystemManual.pdf PDP-11/20 system manual] (DEC-11-HR1B-D)
 ** [http://www.bitsavers.org/pdf/dec/pdp11/1120/1120_SystemSchems_Feb70.pdf PDP-11/20 Engineering Drawings]
 * [http://gordonbell.azurewebsites.net/Digital/PDP%2011%20Handbook%201969.pdf pdp11 handbook] - PDP-11/20 Processor Handbook
 * [https://vintagecomputer.net/digital/PDP11-20/PDP11_Brochure_1970Feb.pdf pdp11] - DEC brochure
 * [https://vintagecomputer.net/digital/PDP11-20/PDP11_Articles_1970Jan.pdf PDP-11 rides on a unibus] - announcement press coverage

@@ Line 74: / Line 74: @@
 ** [http://www.bitsavers.org/pdf/dec/pdp11/1120/1120_SystemSchems_Feb70.pdf PDP-11/20 Engineering Drawings]
 * [http://gordonbell.azurewebsites.net/Digital/PDP%2011%20Handbook%201969.pdf pdp11 handbook] - PDP-11/20 Processor Handbook
 * [http://hampage.hu/pdp-11/1120.html PDP-11/20, /15]

@@ Line 2: / Line 2: @@
 | name = PDP-11/20
 | manufacturer = [[Digital Equipment Corporation]]
-| introduced= 1970
+| architecture        = [[PDP-11]]
-| bus arch = [[UNIBUS]]
+| year announced      = January, 1970
 }}
-[[Image:PDP11-20.jpg|right|150px|thumb|PDP11/20]]
+[[Image:PDP11-20.jpg|left|200px|thumb|PDP11/20]]
 The PDP-11/20 was the first [[PDP-11]] from [[Digital Equipment Corporation|DEC]]; its [[KA11 CPU]] was built from a set of [[DEC card form factor|quad width extended-length]] cards carrying SSI [[transistor-transistor logic|TTL]] [[integrated circuit|chips]], along with a few dual width cards. It introduced the [[UNIBUS]] as a universal path to connect together the [[Central Processing Unit|CPU]], [[main memory]] and [[peripheral|devices]].
@@ Line 19: / Line 38: @@
 One was a [[co-processor]] for the multiply/divide functions, the [[KE11-A Extended Arithmetic Element]]; rather than additional [[instruction]]s in the CPU, it was implemented as a [[peripheral|device]] on the [[bus]], making this model somewhat incompatible with the rest of the PDP-11's.
-The KS11 was apparently DEC's first attempt at an add-on to provide memory management to the -11/20. Other than a [https://www.bell-labs.com/usr/dmr/www/odd.html funny story], nothing is known of it. The extremely rare [[KT11-B Paging Option]] was logically an addition to the CPU, interposed between the KA11 and the UNIBUS (but also having a few ties into the CPU); it allowed [[hardware]]-based [[time-sharing]], and use of up to the full 248 KBytes of memory addressable by the UNIBUS.
+The [[KS11 Memory Protection and Relocation option|KS11]] was apparently DEC's first attempt at an add-on to provide memory management to the -11/20. Other than a [https://www.bell-labs.com/usr/dmr/www/odd.html funny story], little is known of it. The extremely rare [[KT11-B Paging Option]] was logically an addition to the CPU, interposed between the KA11 and the UNIBUS (but also having a few ties into the CPU); it allowed [[hardware]]-based [[time-sharing]], and use of up to the full 248 KBytes of memory addressable by the UNIBUS.
 ==Software==

@@ Line 55: / Line 55: @@
 ** [http://www.bitsavers.org/pdf/dec/pdp11/1120/1120_SystemSchems_Feb70.pdf PDP-11/20 Engineering Drawings]
 * [http://gordonbell.azurewebsites.net/Digital/PDP%2011%20Handbook%201969.pdf pdp11 handbook] - PDP-11/20 Processor Handbook
 {{PDP-11}}
 [[Category: UNIBUS PDP-11s]]

@@ Line 44: / Line 44: @@
 Trivia: The machine was set to be named "PDP-11/30" originally, but it was renamed to 11/20 because of the similar designation of the IBM 1130.
 </i>
 ==External links==

@@ Line 7: / Line 7: @@
 [[Image:PDP11-20.jpg|right|150px|thumb|PDP11/20]]
-The PDP-11/20 was the first [[PDP-11]]; its [[KA11 CPU]] was built from a set of [[DEC card form factor|quad width extended-length]] cards carrying SSI [[transistor-transistor logic|TTL]] [[integrated circuit|chips]], along with a few dual width cards. It introduced the [[UNIBUS]] as a universal path to connect together the [[Central Processing Unit|CPU]], [[main memory]] and [[peripheral|devices]].
+The PDP-11/20 was the first [[PDP-11]] from [[Digital Equipment Corporation|DEC]]; its [[KA11 CPU]] was built from a set of [[DEC card form factor|quad width extended-length]] cards carrying SSI [[transistor-transistor logic|TTL]] [[integrated circuit|chips]], along with a few dual width cards. It introduced the [[UNIBUS]] as a universal path to connect together the [[Central Processing Unit|CPU]], [[main memory]] and [[peripheral|devices]].
-It was the only one to use discrete logic for its control circuits, as opposed to [[microcode]] (this was because the cheap, fast [[read-only memory|ROMs]] needed for economical implementation of that approach did not exist yet at the time it was designed).
+It was the only PDP-11 to use discrete logic for its control circuits, as opposed to [[microcode]] (this was because the cheap, fast [[read-only memory|ROMs]] needed for economical implementation of that approach did not exist yet at the time it was designed).
 The CPU consisted of two and a half quad [[system unit]] [[backplane]]s (the two otherwise-unused slots were [[Small Peripheral Controller|SPC]] slots, available for any [[peripheral]]) [[wire-wrap]]ped into a single unit (see [[KA11 CPU#Implementation|here]] for details). They, and the [[KY11-A Programmer's Console|KY11-A]] [[front panel]], were mounted in a [[BA11-C Mounting Box]].
@@ Line 19: / Line 19: @@
 One was a [[co-processor]] for the multiply/divide functions, the [[KE11-A Extended Arithmetic Element]]; rather than additional [[instruction]]s in the CPU, it was implemented as a [[peripheral|device]] on the [[bus]], making this model somewhat incompatible with the rest of the PDP-11's.
-The KS11 was apparently DEC's first attempt at an add-on to add memory management to the -11/20. Other than a [https://www.bell-labs.com/usr/dmr/www/odd.html fuuny story], nothing is known of it.
+The KS11 was apparently DEC's first attempt at an add-on to provide memory management to the -11/20. Other than a [https://www.bell-labs.com/usr/dmr/www/odd.html funny story], nothing is known of it. The extremely rare [[KT11-B Paging Option]] was logically an addition to the CPU, interposed between the KA11 and the UNIBUS (but also having a few ties into the CPU); it allowed [[hardware]]-based [[time-sharing]], and use of up to the full 248 KBytes of memory addressable by the UNIBUS.
 ==Software==
-An -11/20 was the first PDP-11 to run [[UNIX]], albeit a very early version.
+The -11/20 was the machine that [[RSTS/E|RSTS]] (called 'RSTS-11' when it was on the -11/20) ran on. Many other DEC PDP-11 [[operating system]]d (e.g. [[DOS-11]]) started out on the -11/20.
 == hampage.hu ==
@@ Line 46: / Line 47: @@
 ==External links==
 * [http://gordonbell.azurewebsites.net/Digital/PDP%2011%20Handbook%201969.pdf pdp11 handbook] - PDP-11/20 Processor Handbook