Re: These days what percentage of a CPU's work involves doing arithmetic computations versus other, non-arithmetic computations?

"Robin Vowels" <robin51@dodo.com.au>
Fri, 16 Jul 2021 14:47:25 +1000

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From: "Robin Vowels" <robin51@dodo.com.au>
Newsgroups: comp.compilers
Date: Fri, 16 Jul 2021 14:47:25 +1000
Organization: Compilers Central
References: 21-07-004 21-07-006
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Keywords: history, architecture
Posted-Date: 16 Jul 2021 12:06:36 EDT

----- Original Message -----
From: "gah4" <gah4@u.washington.edu>
Sent: Thursday, July 15, 2021 7:31 PM


> On Wednesday, July 14, 2021 at 12:42:37 PM UTC-7, Roger L Costello wrote:
>> Hello Compiler Experts!
>
>> As I understand it, computers were originally designed to do arithmetic
>> computations and in the old days nearly 100% of a CPU's work involved
>> arithmetic computations.
>
> It seems that people might have believed that, even for a long time, but
> I suspect rarely true.
.
Certainly early computers were designed to perform numerial computations.
From ENIAC, which was designed to compute range tables, Pilot ACE, DEUCE
and most others were all designed to perform numerical work.
They were intended to take over the work of computors (those who used
mechanical caculating machines), and designed to reduce the time taken
to carry out numerical computations.


> There are stories about the IBM 704 Fortran compiler,
> and the authors believed that they had to make optimal use of the hardware,
> or no-one would use their compiler. At the time, that would have been
> assembly programmers, in some for or other.


In the early days, there was no assembler. It was all machine code,
laboriously crafted by programmers.


> Then when they were testing
> the compiler, they were surprised at the code generated doing things
> better than they thought of doing.
>
> Early computers were sold with minimal, if any, software.


That's not true. For the DEUCE, over 1,000 programs and subroutines
were published by The English Electric Company and distributed free
to the owners of their computers. Many of these programs and subroutines
were designed by the users (customers). The cards occupied several
punch card cabinets holding about 50,000 cards, while the writeups
(user manuals) occupied a couple of filing cabinets. Everything was in
duplicate.


For SILLIAC, a large handbook containing programs and subroutines
was published.


For the S/360 cited, IBM published volumes of scientific subroutines
in both FORTRAN and PL/I.
[On the other hand, the first commercial computers, LEO in the UK and
Univac in the US, were used for business work which involved only
modest amounts of arithmetic. IBM's 701 "defense calculator" was
primarily for arithmetic but the 702 was character addressed for
business use.
The goal of S/360 was to unify IBM's product lines
so there'd be only one set of hardware and operating system for
commercial and scientific use. Memory limits soon forced multiple
operating systems (BOS, DOS/TOS, OS) but I gather that on all of them
the most used application was sort/merge. -John]



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