Re: Recipes?

On Tue, 12 Jan 1999, Terry Carroll <carroll[_at_]tjc.com> wrote:
>
> "Word" is ambiguous and varies by architecture. It's generally
> a grouping of more than one byte, so I'm surprised at the above
> description. In the IBM 360/370/390 architecture, a word is
> 4 bytes (32 bits); units of 2 bytes (16 bits) are called "halfwords"
> and units of 8 bytes (64 bits) are called "doublewords."

I would guess that the commercial sucess of this architecture is one reason that word sizes and byte sizes are powers of two for the vast majority of computers and processors sold today. Prior to this, IBM too used various word sizes.  

> I think that, on the Intel and Motorola architectures, a "word" is
> two bytes (16 bits).

This is pretty common for most older mini and micro architectures (many of which were built on the Moto 6800/68k).

> "Byte" is almost (but not quite) universally 8 bits.
>
> I believe the Univacs of the '60s and '70s had 36-bit words (four
> nine-bit bytes, as I recall).

Actually, things are/were a bit more varied. I am sure that I am going to leave some stuff out here, but here goes:

word size char size chars/word architecture Company

--------- --------- ---------- ----------  ------------------
16 bits    8 bits       2      Mini/Micro  Intel,Moto,DEC,DG
24 bits    6 bits       8      PDP??       DEC
24 bits    ??????       ?      DSPs        TI,Moto
36 bits    6 bits       6      1100        Univac/Sperry/Unisys
36 bits    6 bits       6      GCOS 8      GE/Honeywell/Bull
36 bits    9 bits       4      1100/2200   Sperry/Unisys
36 bits    9 bits       4      GCOS 8      Honeywell/Bull
48 bits    6 bits       8      A/B series  Burroughs/Unisys
48 bits    8 bits       6      A/B series  Burroughs/Unisys
60 bits    6 bits      10      6000        CDC
60 bits    7 bits       8      6000        CDC

It should be noted that most of these architectures are still being manufactured (the exceptions I believe are CDC and the PDP). The companies separated by "/" indicate sucessive ownership of the architecture.

-- 
--------------------------------------------------------------------
The preceding was not a legal opinion, and is not my employer's.
Original portions Copyright 1998 Bruce E. Hayden,all rights reserved
My work may be copied in whole or part, with proper attribution,
as long as the copying is not for commercial gain.
--------------------------------------------------------------------
Bruce E. Hayden                      bhayden[_at_]acm.org
Phoenix, Arizona                     bhayden[_at_]ieee.org
                                     bhayden[_at_]copatlaw.com