Re: Fat references

glen herrmannsfeldt <gah@ugcs.caltech.edu>
Sat, 2 Jan 2010 20:20:45 +0000 (UTC)

          From comp.compilers

Related articles
[7 earlier articles]
Re: Fat references jon@ffconsultancy.com (Jon Harrop) (2009-12-30)
Re: Fat references gah@ugcs.caltech.edu (glen herrmannsfeldt) (2009-12-31)
Re: Fat references jon@ffconsultancy.com (Jon Harrop) (2010-01-01)
Re: Fat references cr88192@hotmail.com (BGB / cr88192) (2010-01-01)
Re: Fat references cr88192@hotmail.com (BGB / cr88192) (2010-01-01)
Re: Fat references anton@mips.complang.tuwien.ac.at (2010-01-02)
Re: Fat references gah@ugcs.caltech.edu (glen herrmannsfeldt) (2010-01-02)
Re: Fat references bobduff@shell01.TheWorld.com (Robert A Duff) (2010-01-02)
Re: Fat references jon@ffconsultancy.com (Jon Harrop) (2010-01-03)
Re: Fat references DrDiettrich1@aol.com (Hans-Peter Diettrich) (2010-01-03)
Re: Fat references bear@sonic.net (Ray) (2010-01-03)
Re: Fat references anton@mips.complang.tuwien.ac.at (2010-01-03)
Re: Fat references gah@ugcs.caltech.edu (glen herrmannsfeldt) (2010-01-03)
[15 later articles]
| List of all articles for this month |

From: glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups: comp.compilers
Date: Sat, 2 Jan 2010 20:20:45 +0000 (UTC)
Organization: California Institute of Technology, Pasadena
References: 09-12-045 09-12-055 10-01-003 10-01-008
Keywords: architecture, history
Posted-Date: 03 Jan 2010 14:39:08 EST

Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
(snip, someone wrote)


>>> 16 bits: word
>>> 32 bits: double word
>>> 64 bits: quad word


(then I wrote)
>>That is VAX. Everyone else uses 32 bits for a word.


> No, that's the 8008 and its successors. For the PDP-11 and its
> successors (including the VAX) the 32-bit units were called longwords.


Certainly the PDP-11 was described as having a 16 bit word, but I
don't remember double word, or especially quad word being used in
context with the PDP-11. There were no memory operations that would
do that.


The 8008, 8080, 6800, 6502, and others at that time were considered
'eight bit processors' even though the 8080 could do some 16 bit
operations. One might have called 16 bits a word, but it wasn't
commonly needed. (At least much less than for the PDP-11.)


Already being used to a 32 bit word for S/360, I remember being
disappointed at the time that VAX called 16 bits a word. Especially
if one believed that VAX was supposed to be in the 32 bit processor
marketplace.


> "Word" for 32 bits is common for architectures that originated from
> 32-bit architectures that were not sold as extensions of 16-bit or
> 8-bit architectures (e.g., IBM 360, MIPS, SPARC, ARM).


It always made some sense to me. As I remember, in typing a word is
considered to be five characters. The average english word seems
likely to be in the four or five character range, not two.


> How do original 64-bit architectures like the Cray-1 call 16-bit and
> 32-bit units? Do they have any support for that at all?


I believe the Cray-1 does 64 bit memory operations, and that most (if
not all) C compilers for the Cray-1 used a CHAR_BIT of 64. If C char,
short, int, and long are all 64 bits, why have a name other than word
for them?


-- glen



Post a followup to this message

Return to the comp.compilers page.
Search the comp.compilers archives again.