Questions tagged [pdp-11]
For questions regarding the DEC PDP-11 minicomputer.
72
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Bug in PDP-11/23 Plus diagnostic JKDIB0?
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 ...
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6
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How did the `long` and `short` integer types originate in C?
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-...
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Hierarchical/navigational database engine available on RSX-11M
Around 1988-1990 I worked for a company that was using an old RSX-11M system to host an ERP application. The application used a third-party database product of which I am trying to recall the name. ...
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6
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1
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In the RL02 disk system, why does the “read” command take CHS coordinates, when there is also a separate “seek” command?
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....
3
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1
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Why does this code trigger a TRAP on a PDP11/70?
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....
3
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0
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DEC (probably PDP-11) operating system with a guest mode allowing to run BASIC programs
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 ...
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1
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1
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When was the PDP-11/50 released?
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?
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11
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Why did the VAX compatibility mode not implement the MARK instruction?
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 ...
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5
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1
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Why is the start address in the PDP-11/23(+) micro-ODT a 18-bit address?
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-...
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1
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1
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Interrupt latency on the PDP-11/23
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 ...
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PDP-11 Program to Execute Only in the Registers
The contents of processor registers of a PDP-11/05, etc were available at UNIBUS memory addresses and it was possible to execute a small test program just in the processor registers without accessing ...
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2
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What encoding is this BK-0010-01 FOCAL file in?
I want to keep copies of the programs I write in BK FOCAL on my modern laptop, and in the end to be able to transfer text file programs to the BK.
My current system for transferring files between the ...
- 2,963
11
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4
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What is the difference (if any) between these two expressions in FOCAL?
I am trying to understand the 1969 FOCAL program Hamurabi in detail. The program was originally written for the PDP-8 version of FOCAL, but I am running it on the BK 0010-01 which presumably is a ...
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9
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Was the design of the PDP-11 Floating Point Processor responsible for C's willingness to do arithmetic on floats at double precision?
The Wikipedia page on PDP-11 architecture has a very interesting bullet point in the section on the Floating Point Processor extension to the basic architecture:
full floating point operations on ...
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2
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How to install RSX-11S?
I'm trying to install an RSX-11S system on my LSI-11 (PDP-11/03) simulator. I was under the impression that an RSX-11S system could be generated (via 11SGEN.CMD) from an RSX-11M or RSX-11M PLUS system....
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