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Re: Solving the Floating-Point Goldilocks Problem!

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Morten Reistad <first@last.name> writes:

> In article <d12d6d7d-759d-47ab-b894-cf6ce397301e@z4g2000vbz.googlegroups.com>,
> Quadibloc  <jsavard@ecn.ab.ca> wrote:
>>On Sep 5, 11:48 pm, Patrick Scheible <k...@zipcon.net> wrote:
>>
>>> but also made it very difficult to tell which pieces of memory any given
>>> instruction were going to access in advance.
>>
>>Yes. While the PDP-10 was a wonderful machine, it would not be
>>appropriate for that architecture to be today's standard instead of
>>the x86 architecture - for all of its flaws. It's essential that any
>>modern architecture lend itself well to deep pipelines and arithmetic
>>units designed to work quickly in parallel (i.e. Wallace trees instead
>>of handing the multiplier serially).
>
> The only things I have found that would make a pdp10 non-pipelige
> friendly are related to the effective address calculation, which could
> loop, and was totally unpredictable until the code got there.
>
> If bit 13 (the "@") was set, I cannot see how a pipeline could handle
> it without exploding in complexity.
>
> There are some other smaller things, like aliasing registers as 
> memory locations, indexing with wild abandon (and even sometimes invoking
> "@" there too) and some skips over instructions, but otherwise it
> should lend itself well to pipelining. 
>
> The pipelining could also do "bit 13" excepts, and fall back to a
> stall if this happened.
>
> Advanced pipelining could analyse one step into a "@", and see if
> the chain ended there.

You could, but multiple indirection was heavily used in PDP-10 code.
Pipelining failing in that case means it's less than successful
overall.  My understanding is this is why the Jupiter's performance was
less than hoped.

-- Patrick

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Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-01 13:39 +0000
  Re: Solving the Floating-Point Goldilocks Problem! "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-09-01 08:18 -0700
    Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-02 13:44 +0000
      Re: Solving the Floating-Point Goldilocks Problem! "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-09-02 09:37 -0700
        Re: Solving the Floating-Point Goldilocks Problem! Patrick Scheible <kkt@zipcon.net> - 2011-09-02 10:21 -0700
          Re: Solving the Floating-Point Goldilocks Problem! rpw3@rpw3.org (Rob Warnock) - 2011-09-05 06:11 -0500
        Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-03 14:57 +0000
          Re: Solving the Floating-Point Goldilocks Problem! Peter Flass <Peter_Flass@Yahoo.com> - 2011-09-03 13:13 -0400
            Re: Solving the Floating-Point Goldilocks Problem! rpw3@rpw3.org (Rob Warnock) - 2011-09-05 06:41 -0500
              Re: Solving the Floating-Point Goldilocks Problem! Peter Flass <Peter_Flass@Yahoo.com> - 2011-09-05 08:21 -0400
              Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-05 13:26 +0000
            Re: Solving the Floating-Point Goldilocks Problem! Patrick Scheible <kkt@zipcon.net> - 2011-09-05 22:48 -0700
              Re: Solving the Floating-Point Goldilocks Problem! Quadibloc <jsavard@ecn.ab.ca> - 2011-09-06 16:51 -0700
                Re: Solving the Floating-Point Goldilocks Problem! Morten Reistad <first@last.name> - 2011-09-07 14:14 +0200
                Re: Solving the Floating-Point Goldilocks Problem! Patrick Scheible <kkt@zipcon.net> - 2011-09-07 09:45 -0700
                Re: Solving the Floating-Point Goldilocks Problem! Rob Doyle <radioengr@gmail.com> - 2011-09-07 18:54 -0700
                Re: Solving the Floating-Point Goldilocks Problem! Quadibloc <jsavard@ecn.ab.ca> - 2011-09-08 00:53 -0700
                Re: Solving the Floating-Point Goldilocks Problem! MitchAlsup <MitchAlsup@aol.com> - 2011-09-08 08:00 -0700

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