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Subject: Re: Introducing "No-Moore's Law"

Author: Robert Hyatt

Date: 08:45:20 03/05/03

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On March 05, 2003 at 01:19:12, Jeremiah Penery wrote:

>On March 04, 2003 at 23:06:39, Robert Hyatt wrote:
>
>>On March 04, 2003 at 19:22:50, Matt Taylor wrote:
>>
>>>Nonsense. 486 is all you have to support to be compliant with the full ISA.
>>
>>You remind me of my son.  :)
>>
>>To wit:  when the "walk" light comes on, he is going to walk across the
>>street because he _has_ the right of way.  I keep telling him that he is
>>right of course, and one day he might end up _dead_ right.
>>
>>I personally look before walking regardless of the color of the light.  I look
>>before I leave when a light turns green, to be sure some idiot is not going to
>>run the light and make _me_ "dead right".
>>
>>And that is where we are here.  You want to advertise that a machine is
>>equivalentto intel, but faster and cheaper, feel free.  And if you want to stand
>>on the fine print "but if a program uses cmov without checking the CPUID
>>processor capability bits it is a bad piece of software."  But the _customers_
>>will think the machine is broken, and _they_ are the ones you are trying to
>>market to.  You end up right.  Dead right.
>>
>>There is "right" and there is "right".
>
>When you don't check the CPUID flags before using certain instructions, you are
>the one walking across the street without checking for traffic.


You think the average programmer understands that?  I don't think the average
programmer
even understands assembly language, much less that different processors might
have different
instruction sets even though they are called "compatible".  When AMD says the K6
is compatible
with the PII, but faster/cheaper, then I expect it to be _compatible_.  As will
most software
developers.  How many times have _you_ looked at .S output from gcc to see what
instructions
it produces?  I do it all the time and _I_ didn't think about an "equivalent
cpu" being _almost_
"equivalent".

If everyone was a compiler expert, this might be forseeable.  But they aren't.
And I doubt
most would think that -target=pentiumII would break a processor that is supposed
to be
compatible.

Can I say more?

For the streetlight issue, the streetlight is not hanging over the street in
plain sight.  It is
buried under the light pole, with a door with a combination lock on it that has
to be opened
so it can be seen.  Do you expect John/Jane Doe to know that when there is no
sign on the
pole that says "look here for compatibility issues"???

I don't.



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