All Questions
Tagged with instruction-set pdp-11
6
questions
31
votes
4
answers
4k
views
What motivated the weird boolean instruction repertoire of the PDP-11?
The PDP-11 has seven dyadic instructions (I'm not counting the byte/word varieties separately), which take a full six bits for each of its operands. That's twelve bits to specify the operands, and ...
- 39.3k
19
votes
3
answers
2k
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What is the history of the PDP-11 MARK instruction?
The PDP-11 MARK instruction was intended to be used as part of the standard PDP-11 subroutine return convention. MARK facilitated the stack clean up procedures involved in subroutine exit.
To use it, ...
- 19.4k
22
votes
5
answers
2k
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PDP-11 instruction set inconsistencies
The wiki page PDP-11 architecture has a cryptic paragraph with no references or examples:
Inconsistent instructions
Over the life of the PDP-11, subtle differences arose in the implementation of ...
- 19.4k
10
votes
1
answer
763
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Timing and microcode in the PDP-11/40
I've been trying to figure out how the sequence of microcode instructions as described in the [schematics and ROM listing][1] in the PDP-11/40 (KD11-A Processor) relates to the timings given in ...
- 28.4k
11
votes
3
answers
1k
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Was the PDP-11 coroutine instruction actually used?
In a typical description of the coroutine mechanism it usually mentioned that the PDP-11 instruction set provided a way to effect the coroutine switch by a single instruction, namely
JSR PC,@(SP)+.
...
- 19.4k
50
votes
3
answers
8k
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Why did the PDP-11 include a JMP instruction?
The PDP-11's program counter was addressable in two ways: as a general purpose register or as a memory location.
Still, the PDP-11's instruction set included separate instructions for moving a new ...
- 39.3k