Groups > sci.electronics.design > #453615

Re: big drives

From	Don Y <blockedofcourse@foo.invalid>
Newsgroups	sci.electronics.design
Subject	Re: big drives
Date	2017-03-25 15:14 -0700
Organization	A noiseless patient Spider
Message-ID	<ob6pue$om4$1@dont-email.me> (permalink)
References	(7 earlier) <kl2bdc9jid0ukj8ptvc5m53lg5cmd396ih@4ax.com> <ob5jlh$s0q$1@dont-email.me> <0i0ddc1dokesujr1qfen6ojbrvb72b2ui6@4ax.com> <ob6alq$74v$1@dont-email.me> <fimddclg0mijti8fqhe4jh6q9acju8cml2@4ax.com>

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On 3/25/2017 2:11 PM, upsidedown@downunder.com wrote:
> On Sat, 25 Mar 2017 10:53:42 -0700, Don Y
> <blockedofcourse@foo.invalid> wrote:
>
>> On 3/25/2017 7:54 AM, John Larkin wrote:
>>> The PDP-11 was a 16-bit machine programmed in octal. Because it had 8
>>> registers, octal worked. I could once compile instruction to octal by
>>> sight; I probably still can do some. It fit beautifully.
>
> I programmed a lot of diagnostic code into the PDP-11 using front
> panel (binary) switches. That was quite easy. The problem was entering
> the branch instruction offsets, especially backwards, when you had to
> calculate the negative offset and had to consider the actual value of
> the PC, when the branch was taken.

And, remembering "specialty" opcodes (e.g., INTDS) that didn't fit a nice
"decoding pattern".

>> This was true of a lot of machines.  I used to bit-switch diagnostics
>> into Novas by just writing the code in my head and "assembling" it
>> as the nerve impulses traveled down to my fingertips before hitting the
>> DEP-NEXT toggle.
>
> The Nova was a 74181 ALU chip with steroids :-)
>
>> Worked at a place that had *heated* arguments as to whether to
>> "hand-assemble" code for the Z80 in hex or octal (a large swath
>> of the opcode space -- e.g., all the load/store group -- could be
>> easily mapped onto an octal representation).  I just shook
>> my head and asked:  "Why not let the *machine* remember all
>> those details CORRECTLY and reference things SYMBOLICALLY??"
>
> The 8080 (and hence Z80) are basically octal machines. I do not
> understand why Intel switched to hex after initially using octals.

How is it -- or any machine -- an "octal" machine vs. a hexadecimal
machine vs. a binary machine vs. ...?  Does it process data in groups
of three bits -- instead of four?  or 8?  or 1?

Just because the opcodes were chosen to organize certain "selectors"
(operations, registers, conditions, etc.) in particular groupings
doesn't really mean anything.  The bits in the opcode could have been
arbitrarily scrambled -- the instruction decoder doesn't care where
the bits are "physically" located.

By the time you could purchase a "computer on a chip", the technology
(including toolchains) were affordable enough that the idea of "hand
assembling" code was just silly.  Like refusing to use a calculator because
you spent so much time learning how to do "long division" as a child...

:<

[You see the same sort of thing with HLL programmers trying to hand-optimize
code -- that the compiler can usually do *better* and more accurately]

Thread

big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-21 10:21 -0700
  Re: big drives bitrex <bitrex@de.lete.earthlink.net> - 2017-03-21 13:47 -0400
    Re: big drives George Herold <gherold@teachspin.com> - 2017-03-21 12:42 -0700
      Re: big drives dagmargoodboat@yahoo.com - 2017-03-21 12:55 -0700
        Re: big drives George Herold <gherold@teachspin.com> - 2017-03-21 13:37 -0700
          Re: big drives bill.sloman@ieee.org - 2017-03-21 21:51 -0700
            Re: big drives George Herold <gherold@teachspin.com> - 2017-03-22 07:26 -0700
  Re: big drives Winfield Hill <hill@rowland.harvard.edu> - 2017-03-22 03:38 -0700
    Re: big drives Don Kuenz <g@crcomp.net> - 2017-03-22 14:23 +0000
      Re: big drives David Brown <david.brown@hesbynett.no> - 2017-03-22 16:43 +0100
        Re: big drives Don Kuenz <g@crcomp.net> - 2017-03-22 18:35 +0000
          Re: big drives David Brown <david.brown@hesbynett.no> - 2017-03-23 10:24 +0100
            Re: big drives Don Kuenz <g@crcomp.net> - 2017-03-23 16:11 +0000
              Re: big drives krw@notreal.com - 2017-03-23 13:05 -0400
                Re: big drives Don Kuenz <g@crcomp.net> - 2017-03-23 17:39 +0000
                Re: big drives krw@notreal.com - 2017-03-23 21:05 -0400
                Re: big drives Don Kuenz <g@crcomp.net> - 2017-03-24 03:01 +0000
                Re: big drives krw@notreal.com - 2017-03-23 23:09 -0400
                Re: big drives Don Kuenz <g@crcomp.net> - 2017-03-24 04:15 +0000
                Re: big drives krw@notreal.com - 2017-03-24 22:34 -0400
      Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 12:25 -0700
        Re: big drives dplatt@coop.radagast.org (Dave Platt) - 2017-03-22 13:57 -0700
          Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 16:03 -0700
        Re: big drives krw@notreal.com - 2017-03-22 20:29 -0400
  Re: big drives tabbypurr@gmail.com - 2017-03-22 04:36 -0700
    Re: big drives Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-03-22 08:57 -0400
      Re: big drives Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-22 11:59 -0400
        Re: big drives krw@notreal.com - 2017-03-22 13:23 -0400
          Re: big drives Jon Elson <jmelson@wustl.edu> - 2017-03-22 16:38 -0500
            Re: big drives krw@notreal.com - 2017-03-22 20:31 -0400
            Re: big drives gray_wolf <g_wolf@nospam.com> - 2017-03-23 20:59 -0500
            Re: big drives gray_wolf <g_wolf@nospam.com> - 2017-03-23 21:00 -0500
        Re: big drives Robert Baer <robertbaer@localnet.com> - 2017-03-23 22:21 -0800
    Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-22 07:51 -0700
      Re: big drives krw@notreal.com - 2017-03-22 13:23 -0400
      Re: big drives Robert Baer <robertbaer@localnet.com> - 2017-03-23 22:19 -0800
      Re: big drives tabbypurr@gmail.com - 2017-03-24 04:26 -0700
        Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:38 -0700
    Re: big drives Jon Elson <jmelson@wustl.edu> - 2017-03-22 16:37 -0500
      Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-22 16:07 -0700
        Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 16:21 -0700
          Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-22 16:45 -0700
            Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 23:21 -0700
              Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 13:06 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 16:56 -0700
                Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 17:35 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 21:47 -0700
      Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 16:19 -0700
        Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-22 16:50 -0700
          Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 17:58 -0700
            Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-22 21:00 -0700
              Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-22 22:50 -0700
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 08:27 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-23 12:25 -0700
      Re: big drives tabbypurr@gmail.com - 2017-03-24 04:31 -0700
        Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 06:38 -0700
          Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:41 -0700
            Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 11:38 -0700
              Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 13:55 -0700
              Re: big drives tabbypurr@gmail.com - 2017-03-24 17:14 -0700
                Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 17:41 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 18:00 -0700
  Re: big drives Joerg <news@analogconsultants.com> - 2017-03-23 09:35 -0700
  Re: big drives "Michael A. Terrell" <mike.terrell@earthlink.net> - 2017-03-23 18:38 -0400
    Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-23 16:18 -0700
      Re: big drives Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-23 18:29 -0400
        Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-23 18:38 -0700
          Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-23 18:54 -0700
            Re: big drives pcdhobbs@gmail.com - 2017-03-23 19:16 -0700
              Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-23 19:28 -0700
                Re: big drives pcdhobbs@gmail.com - 2017-03-23 19:55 -0700
                Re: big drives krw@notreal.com - 2017-03-23 23:04 -0400
                Re: big drives pcdhobbs@gmail.com - 2017-03-23 22:00 -0700
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:46 -0700
                Re: big drives krw@notreal.com - 2017-03-24 22:38 -0400
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-23 22:22 -0700
                Re: big drives pcdhobbs@gmail.com - 2017-03-23 23:08 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 00:21 -0700
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 09:00 -0700
                Re: big drives David Brown <david.brown@hesbynett.no> - 2017-03-24 17:14 +0100
                Re: big drives tabbypurr@gmail.com - 2017-03-24 09:19 -0700
                Re: big drives David Brown <david.brown@hesbynett.no> - 2017-03-24 17:47 +0100
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 12:01 -0700
                Re: big drives Jasen Betts <jasen@xnet.co.nz> - 2017-03-24 20:30 +0000
                Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 14:06 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 11:55 -0700
                Re: big drives "Michael A. Terrell" <mike.terrell@earthlink.net> - 2017-03-25 04:00 -0400
                Re: big drives upsidedown@downunder.com - 2017-03-24 22:18 +0200
                Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 14:15 -0700
                Re: big drives Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-25 13:21 +0200
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 07:54 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-25 10:53 -0700
                Re: big drives upsidedown@downunder.com - 2017-03-25 23:11 +0200
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-25 15:14 -0700
                Re: big drives upsidedown@downunder.com - 2017-03-26 12:18 +0300
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-26 03:33 -0700
                Re: big drives Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-26 16:36 -0400
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-26 14:13 -0700
                Re: big drives Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-25 21:04 +0200
                Re: big drives pcdhobbs@gmail.com - 2017-03-24 19:03 -0700
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:53 -0700
                Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 12:12 -0700
                Re: big drives John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 14:20 -0700
                Re: big drives krw@notreal.com - 2017-03-24 22:43 -0400
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 20:10 -0700
                Re: big drives krw@notreal.com - 2017-03-24 23:23 -0400
                Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 22:25 -0700
                Re: big drives Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-25 13:23 +0200
        Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 19:36 -0700
      Re: big drives upsidedown@downunder.com - 2017-03-24 10:14 +0200
        Re: big drives Don Y <blockedofcourse@foo.invalid> - 2017-03-24 01:31 -0700
    Re: big drives John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 16:21 -0700
      Re: big drives "Michael A. Terrell" <mike.terrell@earthlink.net> - 2017-03-24 08:54 -0400

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