Re: Setting architectural features in stone

From	Walter Banks <walter@bytecraft.com>
Newsgroups	comp.lang.c, comp.arch
Subject	Re: Setting architectural features in stone
Date	2016-08-02 20:09 -0400
Organization	Aioe.org NNTP Server
Message-ID	<nnrcnr$267$1@gioia.aioe.org> (permalink)
References	(2 earlier) <nnbh76$kc$1@gioia.aioe.org> <nnch0a$6nr$1@dont-email.me> <cb73fb41-fa4c-445b-83f5-25c5edf4b224@googlegroups.com> <20160728165021.72543369@maxa-pc> <nnn452$548$1@dont-email.me>

Cross-posted to 2 groups.

Show all headers | View raw

On 2016-08-01 5:18 AM, Noob wrote:
> [ Cross-posting to comp.arch where the Mill guru lives ]
>
> On 28/07/2016 16:50, Melzzzzz wrote:
>
>> supercat at casperkitty.com wrote:
>>
>>> The majority of C code written will never need to be targeted for
>>> anything other than a general-purpose reprogrammable microcomputer,
>>> and the overwhelming majority of such devices share a number of
>>> architectural features with the PDP-11:
>>>
>>>   1. Integer sizes are power-of-two multiples of an 8-bit character
>>> type.
>>>
>>>   2. Each size of integer larger than the character type is stored as
>>> two halves in either big-endian or little-endian order.
>>>
>>>   3. A relational comparison between pointers will never have any
>>> effect other than to either indicate that the a particular pointer is
>>> higher or that it isn't, in a fashion that forms a ranking (on some
>>> older computers, the relation tested by equality operators might not
>>> be consistent with that tested by relational operators, but the
>>> relational operators would be consistent among themselves).
>>>
>>>   4. Integer arithmetic operations are performed in sign-agnostic
>>> fashion except for promotion, division, right-shift, and relational
>>> operators; thus the default hardware behavior is two's-complement
>>> silent wraparound.
>>>
>>> Can you suggest any remotely-common general-purpose reprogrammable
>>> microcomputers where any of the above do not apply?

Perhaps not generally available. The eTPU used in engine controllers is 
24 bit data word and sells in the general area of 20M copies a year. (It 
is BTW supported with a C compiler)

I have worked on processors that had 9 bit, 12 bit, 13 bit, 18 bit and 
and several 36 bit words.

I have never worked with a procwessor that did not use 2's compliment
arithmetic.

The 12bit and 13bit processpors had no general provision for byte sized 
character data. The multiple of 9 bit processors all had the ability to 
support 9 bit data.

For what it is worth I am currently working on a project with a non 
power of two multiple of 8 bits that also does not support character 
data in any familliar size.

C often is used as a reason to support charters and power of two data 
sizes but there is no language limit that restricts its use for other 
data formats.

w..

Thread

Re: Setting architectural features in stone Noob <root@127.0.0.1> - 2016-08-01 11:18 +0200
  Re: Setting architectural features in stone Ivan Godard <ivan@millcomputing.com> - 2016-08-01 09:26 -0700
  Re: Setting architectural features in stone anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-08-01 15:48 +0000
  Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-01 10:13 -0700
  Re: Setting architectural features in stone Walter Banks <walter@bytecraft.com> - 2016-08-02 20:09 -0400
    Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-02 18:39 -0700
      Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-03 00:52 -0700
        Re: Setting architectural features in stone Walter Banks <walter@bytecraft.com> - 2016-08-03 06:45 -0400
      Re: Setting architectural features in stone David Brown <david.brown@hesbynett.no> - 2016-08-03 15:02 +0200
    Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-02 19:37 -0700
      Re: Setting architectural features in stone Noob <root@127.0.0.1> - 2016-08-03 10:52 +0200
        Re: Setting architectural features in stone Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-03 11:09 +0100
        Re: Setting architectural features in stone Keith Thompson <kst-u@mib.org> - 2016-08-03 08:51 -0700
        Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-03 09:36 -0700
          Re: Setting architectural features in stone George Neuner <gneuner2@comcast.net> - 2016-08-03 20:30 -0400
          Re: Setting architectural features in stone Noob <root@127.0.0.1> - 2016-08-04 13:06 +0200
            Re: Setting architectural features in stone Bruce Hoult <bruce.hoult@gmail.com> - 2016-08-04 06:39 -0700
              Re: Setting architectural features in stone nmm@wheeler.UUCP (Nick Maclaren) - 2016-08-04 17:40 +0000
      Re: Setting architectural features in stone nmm@wheeler.UUCP (Nick Maclaren) - 2016-08-03 09:40 +0000
        Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-03 09:50 -0700
          Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-03 10:14 -0700
            Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-04 06:11 -0700
              Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-04 06:14 -0700
      Re: Setting architectural features in stone Walter Banks <walter@bytecraft.com> - 2016-08-03 07:03 -0400
        Re: Setting architectural features in stone already5chosen@yahoo.com - 2016-08-03 04:12 -0700
          Re: Setting architectural features in stone already5chosen@yahoo.com - 2016-08-03 04:26 -0700
            Re: Setting architectural features in stone Walter Banks <walter@bytecraft.com> - 2016-08-03 07:50 -0400
          Re: Setting architectural features in stone Walter Banks <walter@bytecraft.com> - 2016-08-03 07:35 -0400
    Re: Setting architectural features in stone anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-08-03 06:42 +0000
      Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-03 00:03 -0700
        Re: Setting architectural features in stone anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-08-03 08:30 +0000
      Re: Setting architectural features in stone Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-03 11:02 +0100
        Re: Setting architectural features in stone Ivan Godard <ivan@millcomputing.com> - 2016-08-03 03:15 -0700
        Re: Setting architectural features in stone anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-08-03 11:53 +0000
          Re: Setting architectural features in stone Quadibloc <jsavard@ecn.ab.ca> - 2016-08-03 18:03 -0700
            Re: Setting architectural features in stone Bruce Hoult <bruce.hoult@gmail.com> - 2016-08-04 01:54 -0700
            Re: Setting architectural features in stone anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-08-04 09:28 +0000
      Re: Setting architectural features in stone timcaffrey@aol.com - 2016-08-04 09:48 -0700
        Re: Setting architectural features in stone Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2016-08-04 10:04 -0700

csiph-web