Questions tagged [instruction-set]
For questions regarding the instruction sets of microprocessors.
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How were Zuse Z22 Instructions Encoded?
The title says it all:
How to En-/Decode Z22/Z23 Instructions?
(History and Linkage:
The question was raised by Wilson in a comment on my answer to his question "Why are PDP-7-style microprogrammed ...
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Why are PDP-7-style microprogrammed instructions out of vogue?
DEC, and at least some of their computers, especially those in the 18-bit family and 12-bit family, had these opr instructions, which contained many bitfields which encoded something like "...
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How did the 8086 interface with the 8087 FPU coprocessor?
The 8087 has many instructions - too many, it seems, to be encoded as part of the 8086 instruction set. How did the Intel 8086 interface with an Intel 8087 FPU that a user added?
Consider the ...
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Was there a Western computer with blatantly missing instructions in the instruction set?
In the BESM-6, there is an instruction (045) to add index registers, but not to subtract them, however, there is a nearby unused opcode 047, which is made synonymous to 045 (in fairness, that's true ...
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What was the main purpose of bitshift instructions in CPU?
As far as I know, even simple RISC microcontroller have a bitshift operator, and honestly I had to use it only once when I had to compute a division on a MCU that could not do divisions in the ALU.
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Operating systems which have non-x86 instruction set architecture [closed]
What are the most famous operating systems for non-x86 computers? I mean, most famous OS which have different instruction set architecture.
Background (to better understand my task):
I ask this ...
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How can floating point addition be so slow on a BESM-6?
In the BESM-6 technical manuals — for example, in the ALU description, page 4 — there is a table specifying min/max/average instruction latencies in clock cycles (the last 3 columns; the ...
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Why does an instruction include the address of the next instruction on the IBM 650?
The IBM 650 seems to be a load-store machine. One advantage of a load-store machine is that the instruction can be shorter because there's less pressure to pack more information into it. But the IBM ...
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Which CPUs had instructions leaving data registers in an unspecified state?
When an ALU performs a floating point division operation using the non-restoring or the SRT algorithm, it maintains the current value of the "remainder" (in quotes, because it is not a true ...
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Which undocumented 8085 instructions is Steven Morse referring to in "In The Beginning"?
In S. P. Morse's 1980 allegory, "In The Beginning", he writes
And Intel said, "Let there be an 8085 with an oscillator on the same chip as the processor, and let an on-chip system controller ...
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What is the instruction set of the Z4?
I am able to find a few instructions, such as:
Fin (presumably "Fine", as in the end of a musical score, ends a program),
Fin', (a conditional Fin),
St (possibly "Start" -- the need for this is ...
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Instruction set support for multiplication with a constant
Before integer multipliers in silicon, several cpus had some support for multiplication. For instance SPARCv7 has the MULScc multiply-step instruction (several other cpus also have this).
As far as ...
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How to keep the instruction prefetcher filled up
My understanding is that the Intel 8088 has this buffer which reads ahead in the instruction stream whenever it has a spare bus cycle or two, so that when the time comes to execute that instruction, ...
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What is the purpose of the ω register of the БЭСМ-6?
This page describing the БЭСМ-6 instruction set refers to a value called ω, which is stored inside a Mode Register. It appears to be set by certain kinds of instructions, so that ω can tell you which ...
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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, ...
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