All Questions
Tagged with instruction-set history
11
questions
40
votes
4
answers
38k
views
Did any processor implement an integer square root instruction?
Has any processor ever implemented an integer square root instruction? Obviously, floating-point square root instructions are quite common, but I've never seen one specifically for integers.
One close ...
- 857
3
votes
0
answers
185
views
What aspects of microprocessor ISAs have been patented?
A key objective of RISC-V was that every aspect of the ISA must be based on an expired patent. It was felt that this is the only truly reliable defense against patent lawsuits.
It is surprising that ...
- 63.1k
4
votes
2
answers
1k
views
What was the first CPU/FPU without a hardware square-rooter?
The first programmable, electronic, general-purpose digital computer, ENIAC had a "square rooter":
five of the accumulators were controlled by a special divider/square-rooter unit to ...
- 19.4k
10
votes
2
answers
548
views
Did any core-memory computers have a read-and-erase instruction?
Magnetic core, the primary form of computer memory from the mid-fifties to the early seventies or thereabouts, had the slightly awkward property that reading it erased it, so every time the CPU ...
- 63.1k
14
votes
2
answers
2k
views
Origin of "arithmetic" and "logical" for signed and unsigned shifts
The assembly language for many processors use the phrase "arithmetic shift" to represent the bitwise shift of a signed value, and "logical shift" for an unsigned value. The two ...
- 16.5k
22
votes
1
answer
1k
views
When did the IBM 650 have a "Table lookup on Equal" instruction?
In 1959, Donald Knuth wrote an assembly program named SuperSoap for the IBM 650. Here is the manual, and here is a listing of the program (in SuperSoap assembly language). Quoting from the abstract:
...
- 3,627
14
votes
2
answers
612
views
What is the purpose of the "difference of absolute values" instruction?
The IBM NORC computer, among others, had an arithmetic instruction computing the difference of the absolute values of its operands (|x|-|y|, see NORC Programming Manual, page 11, opcode 28), which ...
- 19.4k
6
votes
2
answers
1k
views
What’s the last x86 CPU that didn’t place a limit on the size of a single instruction?
Although useless, it’s widely known the first Intel and derivative CPUs like the Z80 didn’t set a limit on the instruction size. This means that it was possible to fill the whole RAM/ROM with a single ...
- 322
19
votes
3
answers
2k
views
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
14
votes
4
answers
2k
views
Are there any articles elucidating the history of the POPCOUNT instruction?
Figuring out how many bits in a group of bits are set to 1, known as computing "population count", Hamming weight, or "bit summation", among others, has various applications.
It is also fairly cheap ...
- 19.4k
8
votes
1
answer
550
views
Was there ever a division instruction with sign of the remainder following the sign of the quotient?
A document about the precursor to ANDF (Architecture Neutral Distribution Format) mentions that two of its integer division/remainder primitives "are those generally implemented directly by processor ...
- 19.4k