Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!elroy!mahendo!jplgodo!wlbr!scgvaxd!trwrb!felix!martin
From: martin@felix.UUCP (Martin McKendry)
Newsgroups: comp.arch
Subject: Re: More than 32 bits needed where?
Message-ID: <20891@felix.UUCP>
Date: 9 Feb 88 01:36:06 GMT
References: <235@unicom.UUCP> <28200089@ccvaxa> <3104@watcgl.waterloo.edu> <19667@bu-cs.BU.EDU> <625@cresswell.quintus.UUCP>
Sender: daemon@felix.UUCP
Reply-To: martin@felix.UUCP (Martin McKendry)
Organization: FileNet Corp., Costa Mesa, CA
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In article <625@cresswell.quintus.UUCP> ok@quintus.UUCP (Richard A. O'Keefe) writes:
>
>The Burroughs B6700 and its successors (I can never remember the latest
>name for these machines, is it "E-mode"?) had 48-bit single precision

The machines are A-series, the instruction set is E-mode.

>arithmetic and 96-bit double precision arithmetic.  Integers were a
>special case of floats, meaning that you got about 11 decimal digits
>(single) or 23 (double).  Having used 48-bit (B6700) and 36-bit (DEC-10)
>machines, even working at the instruction level of both (a friend and I
>had a hacked version of the B6700 Algol compiler which had an equivalent
>of asm("..")), I have never understood why "word-length = a power of two"
>has such a hypnotic effect on people.  

You want to try doing Cobol, or pointer arithmetic, maintaining separate
character and word portions etc?  Its a nightmare.  Dog slow, too.
Burroughs has patents on some pretty nifty divide-by-3 hardware.

Burroughs considered the needs of
>COBOL, and decided that they'd get more value for money by concentrating
>on binary arithmetic and providing fast decimal<->integer conversion.

Actually, this is not exactly correct.  Burroughs went with 48 bits
precisely because they thought it WAS a power of two.  At the time,
characters were 6 bits (1957-8, remember).  I had the pleasure of
researching this during 1986, when I was employed by Burroughs in
Detroit.  At the time, I was examining the performance of the A-series.
Among the issues that arose was the non-power-of-2 wordsize.

>
>If 32 bits isn't enough, why not go to 48 as the next step?

We proposed taking 48 bits to 64.  They laid us off.



--
Martin S. McKendry;    FileNet Corp;	{hplabs,trwrb}!felix!martin
Strictly my opinion; all of it