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

"Robin Vowels" <>
Fri, 16 Jul 2021 15:12:02 +1000

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From: "Robin Vowels" <>
Newsgroups: comp.compilers
Date: Fri, 16 Jul 2021 15:12:02 +1000
Organization: Compilers Central
References: 21-07-004
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Keywords: architecture, history
Posted-Date: 16 Jul 2021 12:09:07 EDT

----- Original Message -----
From: "Roger L Costello" <>
Sent: Thursday, July 15, 2021 4:30 AM

> 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.
> [I don't think it was ever true except perhaps on the ENIAC.

From ENIAC, computers were designed to perform arithmetic
computations. The motivation was to be able to reduce the
amount of time that it was taking to deliver results (compared to
manual methods using mechanical adding machines). At the same
time, it was expected that human errors would be reduced.

(Even earlier, Charles Babbage, appalled by errors in tables
produced by hand methods, designed machines to do
the work.)

> Also, what do
> you mean by arithmetic? Are the additions and multiplications to do indexing
> and array addresssing arithmetic?

Of course.

> If you mean floating point. there wasn't
> any floating point hardware until the IBM 704 in 1954

It is said that the Z3 (1941) was designed with floating-point.

But even if that were not true, floating-point was already in use
in the 1940s at least in the design of the ACE and the Pilot ACE.
Even before a machine as built, those involved were designing
and refining instruction tables (subroutines) for carrying out
numerical work. In the 1950s, floating-point software
(including block floating) was extensively used on Pilot ACE and,
from 1955, on DEUCE.

> but there was plenty of computing before that. -John]
[I don't think the Z3 was ever built other than as a much later
retrocomputing project. Von Neumann apparently considered floating
point for the EDVAC and IAS machine but rejected it as too complex
and anyway doing the scaling in software was easy, which it
probably was if you were Von Neumann. -John]

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