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Re: Distinguishing DOES>

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Albert van der Horst wrote:
> That is patently incorrect. Intel never wanted to move on from 32
> to 64 bits in a compatible way. They had the Itanium. (Same situation
> as the 432. )

Yes, if they hadn't messed up Itanium so badly, AMD would never have 
succeeded.

> Again. The 8086 was designed by one man Stephen Morse. It was
> a clever extension of the 8080 and a reasonable cisc processor,
> but without a shred of thought about future enhancements.
> (I have his book "8086 architecture". It is adamant about a few
> errors and convincing regards design decisions.)
> This processor had three characteristics that where in hindsight
> responsible for the mess we're in. Too CISCy, segmentation, and
> no regards for sufficiently address extensability.
> The pressure to stay compatible was what did it.
> The "real mode" (a real kludge) was absent in 80286 then reinstated
> in the 80386, pressured by mostly Microsoft.

80286 had real mode and protected mode, but to go back from protected 
mode to real mode, you needed to reset the processor, either by telling 
the keyboard controller to do so or by causing a triple fault (which is 
faster, but Microsoft first used the keybord controller hack).  80386 
had the VM mode, which is much more useful than going back to real mode.

>>The ARM ISA is designed by one person, and even then it is one of the
>>more byzantine RISC ISAs, with lots of things cobbled together in one
>>instruction - shifts, conditional execution, normal operations.
> 
> Remember the Novix? It has also those bit-fields. They just go
> directly to parts of the processor that do e.g. shifting.
> That is RISC in my book, direct relation to the hardware without
> much regard to the assembler programmer.

I'm not convinced. ARM's critical path contains shifter+ALU, which means 
the achievable clock rate is significantly slower than competing RISC 
processors (of that time). The newer ARM cores get higher clock rates by 
dividing the execution stage into two stages, if necessary.

> Conditional execution in one instruction is a very powerful speed
> up mechanism. At the time Intel's alternative (complicated multiple
> instruction analysis) was not viable.

Conditional execution looks nice, but having every instruction 
conditional makes out-of-order execution difficult.

ARM64 drops both the integrated shift field and the omnipresent 
conditional execution - there is still conditional execution, but only 
for instructions where it makes sense (branch, select).

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/

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Distinguishing DOES> JennyB <jennybrien@googlemail.com> - 2012-05-03 08:59 -0700
  Re: Distinguishing DOES> Hugh Aguilar <hughaguilar96@yahoo.com> - 2012-05-03 17:23 -0700
    Re: Distinguishing DOES> Zbiggy <zbigniew2011REMOVE@gmail.REMOVE.com> - 2012-05-04 10:47 +0100
      Re: Distinguishing DOES> Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-04 05:12 -0500
        Re: Distinguishing DOES> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-05-04 11:33 +0000
          Re: Distinguishing DOES> Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-04 08:11 -0500
            Re: Distinguishing DOES> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-05-04 16:18 +0000
              Re: Distinguishing DOES> Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-05 02:02 -0500
                Re: Distinguishing DOES> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-05-05 14:16 +0000
                Re: Distinguishing DOES> Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-06 02:53 -0500
                Re: Distinguishing DOES> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-05-05 14:25 +0000
                Re: Distinguishing DOES> BruceMcF <agila61@netscape.net> - 2012-05-05 08:07 -0700
                Re: Distinguishing DOES> Hugh Aguilar <hughaguilar96@yahoo.com> - 2012-05-08 06:23 -0700
                Re: Distinguishing DOES> Bernd Paysan <bernd.paysan@gmx.de> - 2012-05-09 00:25 +0200
                Re: Distinguishing DOES> Hugh Aguilar <hughaguilar96@yahoo.com> - 2012-05-09 01:26 -0700
                Re: Distinguishing DOES> Mark Wills <markrobertwills@yahoo.co.uk> - 2012-05-09 03:18 -0700
                Re: Distinguishing DOES> Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-09 05:29 -0500
                Re: Distinguishing DOES> "Elizabeth D. Rather" <erather@forth.com> - 2012-05-09 07:11 -1000
                Re: Distinguishing DOES> Zbiggy <zbigniew2011REMOVE@gmail.REMOVE.com> - 2012-05-09 22:48 +0100
                Re: Distinguishing DOES> Bernd Paysan <bernd.paysan@gmx.de> - 2012-05-09 23:22 +0200
                Re: Distinguishing DOES> Zbiggy <zbigniew2011REMOVE@gmail.REMOVE.com> - 2012-05-09 23:43 +0100
                Re: Distinguishing DOES> Bernd Paysan <bernd.paysan@gmx.de> - 2012-05-10 00:49 +0200
                Re: Distinguishing DOES> Zbiggy <zbigniew2011REMOVE@gmail.REMOVE.com> - 2012-05-10 11:33 +0100
                Re: Distinguishing DOES> Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-10 10:02 +0000
                Re: Distinguishing DOES> Bernd Paysan <bernd.paysan@gmx.de> - 2012-05-10 15:13 +0200
                Re: Distinguishing DOES> Mark Wills <markrobertwills@yahoo.co.uk> - 2012-05-10 05:07 -0700
                Re: Distinguishing DOES> Hugh Aguilar <hughaguilar96@yahoo.com> - 2012-05-10 22:57 -0700
  Re: Distinguishing DOES> Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-04 12:37 +0000
  Re: Distinguishing DOES> Doug Hoffman <glidedog@gmail.com> - 2012-05-04 10:14 -0400
    Re: Distinguishing DOES> humptydumpty <ouatubi@gmail.com> - 2012-05-04 20:27 +0000
      Re: Distinguishing DOES> Doug Hoffman <glidedog@gmail.com> - 2012-05-05 06:16 -0400
        Re: Distinguishing DOES> JennyB <jennybrien@googlemail.com> - 2012-05-05 07:19 -0700
          Re: Distinguishing DOES> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-05-05 14:55 +0000
            Re: Distinguishing DOES> JennyB <jennybrien@googlemail.com> - 2012-05-07 07:24 -0700
          Re: Distinguishing DOES> Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-06 11:04 +0000
          Re: Distinguishing DOES> Doug Hoffman <glidedog@gmail.com> - 2012-05-06 07:47 -0400
        Re: Distinguishing DOES> ward@megawolf.com - 2012-05-08 04:39 -0700
          Re: Distinguishing DOES> Doug Hoffman <glidedog@gmail.com> - 2012-05-08 07:50 -0400
  Re: Distinguishing DOES> Hans Bezemer <the.beez.speaks@gmail.com> - 2012-05-05 14:24 +0200
    Re: Distinguishing DOES> Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-06 11:09 +0000

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