Archived from groups: comp.sys.ibm.pc.hardware.chips (
More info?)
On Thu, 2 Jun 2005 03:20:46 +0000 (UTC), David Wang <foo@bar.invalid>
wrote:
>George Macdonald <fammacd=!SPAM^nothanks@tellurian.com> wrote:
>
>> Then it's a "conspiracy theorist" err, theory. Surely Intel must have
>> looked at some kind of x86-64 at some time prior to AMD but ISTR the word
>> "impossible" or maybe "impractical" being mentioned at one time when they
>> were trying to justify Itanium. Certainly Intel seemed to want *something*
>> of AMD's... or the would never have signed the cross-license agreement of
>> Jan 1, 2001.
>
>At the time of the Intel/HP collaboration, Intel was working on P7,
>which was a 64 bit x86 processor. I do not believe that Intel (or
>anyone representing Intel) would have suggested anything that
>suggests that x86-64 was "impossible" or "impractical". Switching
>from x86-64 ISA to IA64 was not because x86-64 was "impossible" or
>"impractical". It was believed to be "better".
"Better"... but for whom though?
Intel detested the fact that x86 was a
semi-open architecture & ISA and Itanium solved that "problem". I honestly
don't remember the wording but recall that Intel was said to be concerned
about competitiveness with the RISC machines which everybody was raving
about at the time... something which could have been perceived as
impossible.
>When Intel finally decided to do the 64 bit extension to x86, it
>could well have done whatever it wanted to do in terms of
>programming model extension. The problem is ofcourse the guy
>up in NW part of the US put his foot down and says that he'll not
>support yet another ISA from Intel. It would be an interesting
>power struggle, but if BG wants to be bullheaded about it, he wins
>by default. Nothing Intel can do.
Oh I don't think the putting down of the "foot" was entirely due to hubris
as was suggested here recently. M$ had seen several non-x86 WinXX projects
die from lack of err, commitment... by vendors and/or users; the one thing
M$ absolutely needs is volume and I can't believe they are feeling too
happy about Itanium there. Yet another variant to maintain would have been
intolerable - at least one would have to die and by the time Intel threw
its EM64T hat in, AMD64 already had about a year's worth of time invested.
It would certainly be interesting to know to what extent Yamhill, whose
existence was denied for ~18months, started out looking like AMD64. By the
time EM64T was revealed, given where AMD64 was, any attempt to divert
things would have appeared as a capricious act born of umm, hubris. After
all, there's not a lot of different ways you can design a compatible
instruction set - why do it differently?
>> As we already discussed, Cell as we know it, would require a major rework
>> to get above 4GB memory and DP FPU - "doable" I suppose but.....
>
>IBM taped out a new CELL processor with a new PPE. The die size
>grew from 221 mm^2 to 235 mm^2. Compared to that effort, any memory
>system re-work needed to get more memory capacity support is relatively
>minor.
I guess it depends on how high you want to go but to get to 4GB with 512Mb
chips required some fairly fancy footwork already, with different width
memory chips, if I'm remembering things right.
>Also, DP FPU is already in both the PPE and SPE, so I'm not sure what
>you mean by "and DP FPU".
I don't have time to look up the details right now but ISTR that the DP
performance was not even in the same ball-park as the SP - it just wasn't
good enough.
--
Rgds, George Macdonald
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