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From: chuck@amdahl.UUCP
Newsgroups: comp.arch
Subject: Re: 64 Vs 32
Message-ID: <5954@amdahl.UUCP>
Date: Sat, 21-Mar-87 18:07:03 EST
Article-I.D.: amdahl.5954
Posted: Sat Mar 21 18:07:03 1987
Date-Received: Sun, 22-Mar-87 17:39:42 EST
References: <3810013@nucsrl.UUCP> <28200016@ccvaxa> <1308@steinmetz.steinmetz.UUCP> <3436@iuvax.UUCP>
Reply-To: chuck@amdahl.UUCP (Charles Simmons)
Organization: Amdahl Corp, Sunnyvale CA
Lines: 62

In article <3436@iuvax.UUCP> bobmon@iuvax.UUCP (Che' Flamingo) writes:
>davidsen@kbsvax.steinmetz.UUCP (William E. Davidsen Jr) writes:
>>
>>etc. The 68020 and 80386 have enough power to run large
>>businesses, schools, city and county government, etc.

Kinda makes you wonder why the Fortune 500 spends on the order of
$5,000,000 for an IBM mainframe or Amdahl mainframe when 68020
based workstations can be had for on the order of $50,000.

>So I agree that for word size per se, 32 bits is surely adequate; 16 bits is
>probably sufficient for most things that people do (floating point and address
>space are the two exceptions I can think of).

16 bits is clearly not sufficient for most things people do.  Consider
games like rogue which have a tendency toward creative bugs caused by
the fact that some numbers are stored in 16 bit integers as opposed
to 32 bit integers.

Consider any moderately sized company with a gross income of a few
hundred thousand dollars a year.  It would be nice, when generating
reports describing where the money came from and where it went, to
store these figures as fixed point numbers.  But they certainly won't
fit in 16 bit integers.

Any moderately sized database will contain more than 64K records.

I used to use 36 bit integers and had far fewer problems with
integer overflow than people have using 32 bit integers.

Let's think up some applications where 32 bit integers are a little
too small...  People have already mentioned floating point.  How
about the federal government?  Let's see...  they deal with a budget
on the order of a trillion dollars?  100 trillion cents?  I'll bet
they wouldn't mind having a 64-bit bcd word for holding their monetary
variables in their cobol programs.  Even Fortune 500 companies deal
with amounts of money larger than 4 million cents.

How about games?  An othello board can be stored very nicely in
two 64 bit words.  (Actually, 72 bit words work even nicer, but
Honeywell machines are hard to come by.)  Many of the algorithms
for manipulating othello boards are easier to code if you can
perform logical operations on 64 bit words instead of 32 bit
words.

Then there are those people over in net.math who like to look for
godawfully large prime numbers.  I'm sure they wouldn't mind
arithmetic operations on words larger than 32 bits.

By the by...  Amdahl mainframes (and hence probably IBM mainframes
as well) do support 64 bit integers.  Past experience suggests that
anything that exists on a mainframe (cache, virtual memory, time-sharing,
protected address spaces...) will eventually appear on a micro.  Two
items that exist on mainframes, but not yet on micros, are 128-bit data
paths between the cpu and memory, and operations on 64-bit words.

To summarize, there are many current applications that use, or would
like to use, 64-bit words.  When chip makers start building chips
with 64-bit internal data paths, the chips will sell, and the 64-bit
data paths will be useful.

-- Chuck