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Questions tagged [pdp-11]

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For questions regarding the DEC PDP-11 minicomputer.

77 questions
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1 vote
1 answer
309 views

Ok, I know this is a very old computer but just for fun. I have figured out how to read keyboard (0177560 for checking, 0177562 for reading) and print it (0177564 for checking, 0177566 for writing). ...
Codesynth's user avatar
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4 votes
2 answers
223 views

I am searching for information on the operation of the DEC RP04 disk drive. I found several manuals, such as the "RP04 moving head disk subsystem maintenance manual" and the "RP04 ...
JosF's user avatar
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6 votes
3 answers
512 views

There was an implementation of Algol-68 on PDP-11, which is present in the form of raw binary files, allegedly from RSX-11M, and UNIX V7 loaders/adapters for them in the form of Assembly language ...
Leo B.'s user avatar
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14 votes
3 answers
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PDP11 doesn't provide an AND instruction – just XOR. What is the usual PDP-11 assembly code to implement an AND, i.e. the PDP-11 assembler equivalent of the C code a & b please? What I'm looking ...
hptsb's user avatar
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3 votes
0 answers
267 views

What DEC PDP-11 document did these pages come from? Around 1978-1981 I photocopied a section of a DEC PDP-11 document. Now I'm trying to figure out what document that was. The system we had then was a ...
aMike's user avatar
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7 votes
1 answer
207 views

Diagnostic JKDIB0 is one of the PDP-11/23B (aka as PDP-11/23 Plus) diagnostics that tests the behaviour of the BDV11 line time clock (LTC). It specifically contains the following code from address ...
JosF's user avatar
  • 423
19 votes
6 answers
6k views

I was wondering why C has the long and short integer type in addition to the plain int, and came across the following quote in the C99 Rationale (thanks to this answer here): [...] In the 1970s, 16-...
user51462's user avatar
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3 votes
2 answers
303 views

Around 1988-1990 I worked for a company that was using an old RSX-11M system to host an ERP (Enterprise Resource Planning) application. The application used a third-party database product of which I ...
Anthony X's user avatar
  • 501
6 votes
1 answer
547 views

Why is it that the RL02 disk system of the PDP11 has a seek command yet the read command also knows where to read from as the cylinder/head/sector are given via the 'DAR' register? http://www....
Folkert van Heusden's user avatar
  • 417
3 votes
1 answer
659 views

On the PDP11/70, in the XXDP BKTCB0.BIC program I saw the following code: 012716 177777 mov #-1,(KSP) 006627 MTPI (PC)+ According to the comments in the source-code, this triggers a trap....
Folkert van Heusden's user avatar
  • 417
3 votes
0 answers
291 views

In the mid 1970's I used an OS on DEC equipment (I believe PDP-11) that had a guest mode. If you weren't an authorised user you could login as guest mode where you supplied a name and if it didn't ...
hptsb's user avatar
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1 vote
1 answer
218 views

I've seen varying dates for the PDP-11/50 release, ranging from "sometime in 1975" to "June 1976, at the same time as the PDP-11/55." What was the actual date of release?
cjs's user avatar
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11 votes
3 answers
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This question was inspired by an older question about the MARK instruction which recently bubbled up to the top of the active pile. The VAX-11/780 and several follow-on VAXen implemented a PDP-11 ...
dave's user avatar
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5 votes
1 answer
456 views

The KDF11 processors (as used in the PDP-11/23 and PDP-11/23+) contain an 18-bit implementation of ODT, called Micro-ODT. Micronote 058 states that the standard start address for a large (18- or 22-...
JosF's user avatar
  • 423
1 vote
1 answer
208 views

I'm trying to understand the interrupt latency on the PDP-11/23 (more specifically the KDF11-A). Diagnostic JKDBD0 test 375 (Test that a TTY interrupt causes an overflow trap) contains the following ...
JosF's user avatar
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