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

Author: Robert Hyatt

Date: 09:22:09 03/11/03

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On March 10, 2003 at 19:56:12, Jeremiah Penery wrote:

>On March 09, 2003 at 22:10:06, Robert Hyatt wrote:
>
>>On March 09, 2003 at 01:26:33, Jeremiah Penery wrote:
>>
>>>On March 08, 2003 at 23:58:37, Robert Hyatt wrote:
>>>
>>>>On March 08, 2003 at 14:52:02, Jeremiah Penery wrote:
>>>>
>>>>>By selling them side-by-side, Dell is comparing them.  But Pentium3 is not quite
>>>>>a Pentium4 in fact...
>>>>
>>>>And nobody assumes that.
>>>
>>>People assume P3=P4 (in terms of compatibility) just as much as they assume
>>>K6=P2.
>>
>>Maybe some do.  But I'd suspect most don't although the assumption that
>>executables compiled and running on a PIII will also run on a PIV is a
>>good assumption.
>
>I'm quite sure that almost everyone assumes they are 100% compatible.  Some kind
>of poll could be useful, otherwise both of us are just guessing.
>
>>>>But clearly if someone compares a chip to a PII,
>>>>the implication is that they are equivalent.  Otherwise the comparison is
>>>>not very informative.
>>>
>>>I've seen P4 compared to 486, but that doesn't mean anyone should assume they're
>>>totally compatible.  Just like you can compare an Alpha to a SPARC.
>>>
>>>But the P3-P4 comparison is much more relevant.  They're placed side-by-side
>>>_all the time_, and very clearly is it implied that they're equal except that
>>>the P4 is clocked much higher.  The average buyer is NOT going to know the
>>>difference, any more than they knew the difference between a P2 and a K6.
>>
>>Did you see an advertisement where someone was trying to convince you to
>>buy over the other?  I doubt it.
>
>When P3 and P4 existed concurrently, every single ad where Intel advertised the
>P4, they were trying to get you to buy P4 over P3.  Of course they didn't
>explicitly say so, but I don't ever remember seeing an AMD ad where they
>explicitly mentioned an Intel chip either.  The P3 was, for many things, faster
>than the higher clocked P4.  Intel prematurely killed the P3 because they wanted
>to sell P4s, and P3 could have made P4 look bad.

You are arguing this from the _wrong_ side.  The PIV is 100% compatible with the
PIII.  The inverse is _not_ true, and this is often referred to as "backward
compatibility".

That is _different_ than their trying to sell a PIII and saying it is equal to
the PIV but
much cheaper.  And that case is closest to the K6 vs PII point.



>
>>>>It was the _users_ that assumed that PII = K6 since AMD magazine publicity
>>>>certainly implied it if not outright claimed it.
>>>
>>>They imply that P3=P4 too, in terms of compatibility, but they're not completely
>>>so.
>>
>>Again, it depends.  If I do a target=P3, I would expect that to run on a PIV.
>
>If I do target=Pentium, I'd expect it to run on a K6.  That's basically the
>comparison you're making there.

No, I bought a PII and did "target=pentiumII" because _ knew_ that the PII had
different optimization isues than the original pentium.  The PII had an OOE core
for example, while the original pentium depended on the compiler to pair
instructions
for the super-scalar execution units.  At the time I bought a PII, AMD was
advertising
their chip as faster and cheaper.  And it did _not_ say (but not 100%
compatible) and
that led to the confusion I mentioned.



>
>>And most likely if I do a target=p4 it would run on a P3 although I can
>>certainly think of reasons why it wouldn't.
>
>Most of the time it would, just as most of the time K6 would run P2 executables.
> The only difference I'm aware of (for K6/P2) is CMOV.  For P3/P4 the difference
>is SSE2.

But _if_ you compile for the PIII it will absolutely run on the PIV.  If you
compile for
the PIV it will run on the PIV but perhaps not on the PIII depending on the
instructions
the compiler is capable of producing.  However, _nowhere_ did you see Intel say
"The
PIII is 100% compatible with the PIV".  You will find "The PIV is 100% backward
compatible with the Pentium processor product line."



>
>>But Intel doesn't market the P3 to be compatible with the P4.
>
>No.  They market P4 to be compatible with P3.

Playing word games.  "backward compatible" is not "compatible".

look at their ads.  It's very clear what they are saying and what it means.



>
>>>Why don't you use Sun's compiler, which is really fast for SPARC anyway?
>>
>>Because we don't buy it.  It's not cheap and we have so many gcc-based machines
>>we felt the compatibility between compilers was better than the cost of buying
>>Sun's compiler.  We used to have it years ago, and yes, I found it to be a
>>bit better than GCC.  But eventually GCC started producing code that was as fast
>>as Sun's so we dropped sun's compiler.
>
>Seems GCC doesn't do so well anymore. :p

Nope.  But when sun became "pseudo-64bit" their compiler started to suck badly.
 I'm
not sure what Sun thinks they are right now.  Most of the operating system is
_still_ 32 bit
code.




>
>Oh well, I was more interested in the sales numbers (which I haven't yet seen
>:)than the benchmarks anyway.



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