On Wed, 18 Apr 2018 09:46:30 +0100, Gareth's Downstairs Computer
 declaimed the following:

>In the days of DEC minicomputers, one had a
>Programmer's Card which showed all the instructions
>in their binary form. (I've still a couple for
>the PDP11 in the archive somewhere)
>
>Is there such a summary available for the 64 bit
>instruction set of the Pi3's A53 processors?
>
 Other than a few pages in the spec-sheet -- unlikely...

 In a way, modern processors aren't meant to be programmed at the
assembly level. One pretty much needs the backend of a compiler
optimization to get anything usable -- with the result that only the
compiler authors tend to need to know the target instruction set, and they
may be working from a machine-readable specification to automate that step
too.

 It doesn't help that the ARM instruction set has become something that
makes the Xerox Sigma-6 mainframe from my college look like a RISC
processor! I mean, look at this ARM example

ADD W0, W1, W2, LSL #3

One destination register, TWO source registers, and a shift operation to be
applied to the value of the second source register! The only thing making
that remotely RISC is that none of the source/destination are memory
addresses -- and the ARM requires separate load/store operations to touch
memory

Sigma-6, from memory (my manuals are in storage) would take

LD,0 2 ;copy register 2 to register 0
LSLI,0 #3 ;left shift register 0 by immediate value
ADD,0 1 ;add register 1 to register 0

(instruction format is:
 OpCode,register  [*]address[,ir]
where address 0-15 map to register 0-15 or can be a 17-bit immediate value
rather than address; optional * indicated one-level indirect addressing
[use the value found at address as the actual address to operate upon], and
ir was an optional index register [1-7] holding an offset from the
address).

 If the arguments weren't in registers one would get (ARM)

LDR W1,arg1address
LDR W2,arg2address
ADD W0, W1, W2, LSL #3
STR  W0,resaddress

vs (Sigma)

LD,0 arg2address
LSLI,0 #3
ADD,0 arg1address
ST,0 resaddress


https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwjDos
_u_cPaAhWJ6IMKHc-2Cf0QFggxMAI&url=https%3A%2F%2Fwww.element14.com%2Fcommunity%2
Fservlet%2FJiveServlet%2FpreviewBody%2F41836-102-1-229511%2FARM.Reference_Manua
l.pdf&usg=
AOvVaw0FgDRAA4A8TZCL2bJVk6O2
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0024a/ch05s01.ht
ml
(PDF download at bottom of page -- 296page document, nearly 3X the previous
document)



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 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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