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<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">This discussion has very much
diverged from the original topics of VAX/VMS and ISA compatibility. If folks want to discuss the actions or
inactions, who did what <i>etc</i>… let’s
take that off list.</span></p>
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<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">I will try to come back to
what I started with: Some people on this list (including me), believe that
Intel has done a pretty reasonable job of compatibility as it moved from
generation to generation from its original 4004 microprocessor to today’s
Intel*64 ISA From reading the comments,
others may not think the Intel team did, fair enough. Also,
other firms such as IBM and DEC had done the same with their ISA (S360 and Vax
in those cases).</span></p>
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<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">As has been pointed out, each
of three firms mentioned have injected some level of incompatibility along the
way. The question of how a good a job
they did is likely to be gauged on how it affected you personally. I personally find the ability to be able to
boot a really old OS and run really old programs on a modern chip to be
handy. Since this is a forum on
simulation, I would have thought others considered that a pretty important
feature. But maybe it is not. To
pick on DEC (or IBM), the later generations of their respective ISAs cannot
boot the older OS – which Intel’s primary ISA can – and that is what started
this discussion. </span></p>
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<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">I have also pointed out (as have others) that
Intel also did not try to be compatible with all its lines, which others consider that a negative for Intel’s commitment to
compatibility. </span></p>
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<p class="MsoNormal"><span style="font-family:arial,helvetica,sans-serif;font-size:16pt">In fact is in almost every
case except one that I can think, when Intel broke away </span><span style="font-family:arial,helvetica,sans-serif;font-size:21.3333px">from the </span><span style="font-family:arial,helvetica,sans-serif;font-size:16pt">compatibility path that
became today's INTEL*64 ISA, Intel was not as successful in the market (I'm thinking i432, 860, 960, Itanium) – the one success I can think of where they were not
compatible and were still successful was in their embedded line which was
originally the 8748 (which became the 8051).</span><span style="font-family:arial,helvetica,sans-serif;font-size:16pt">
</span><font face="arial, helvetica, sans-serif"><span style="font-size:16pt">I </span><span style="font-size:21.3333px">suppose</span><span style="font-size:16pt"> it also can be pointed out that the 860/960 ended up have a
fairly long life also in the embedded space and were "successful" there.</span></font><span style="font-family:arial,helvetica,sans-serif;font-size:16pt">
</span><span style="font-family:arial,helvetica,sans-serif;font-size:16pt">But those ISAs were eventually EOL’s; while you can still find 8051 ISA
based chips being manufactured today.</span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">Others in this list seem to
object to the fact the current INTEL*64 ISA is owned and defined by Intel, not by
a competing firm who originally created an extension to the x86 (ney IA-32) ISA
before Intel and brought it to market in their product line. Fair enough and I personally think I understand
why people might believe that and I do understand and lived the same history. But I
point out that it does not change the fact that Intel owns and defines ISA, it >>is<<
Intel’s ISA. Someone else does not get to call it
something else when they do not own it. Just
as the PDP-11, Vax & Alpha were DEC’s ISAs and S360, S/370 & Power
is/was IBM’s.</span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">Think about 2 other
instances, Cal Data extended the PDP-11 before DEC did and Amdahl the S/360
before IBM. As it turns out, DEC sued and put Cal Data
out of business but IBM let Amdahl be.
In both cases features first pioneered on those other product lines, end
up in the original (although maybe with a different name and/or different
implementation). But the ISA stayed
S/360 and PDP-11 and the owners of each further extended their ISA along the
way (S/370, now zSeries, PDP-11 begat VAX 11/780).</span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">I ask you for a minute to
consider this set of facts. When the engineers at Intel did decide to extend IA32 to 64 bits (which was after others had done it), the Intel engineering team could have created a set of
extensions to the x86 family that was different from others currently on the market. We can all guess, but none of us on this list or elsewhere will
ever know if taking that design choice would have been successful -- as that choice was made 15 years
ago. I think we might agree that a good bit of chaos would have been brought to us as programmers.</span></p><p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"><br></span></p><p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">Instead, the Intel engineers started
with an existing set of extensions, and added too (and continued to add too) that list. Intel has brought out many devices since that time and the market
has moved on. The choices made by the Intel team does not lessen or
make greater the work done by Intel or it’s competitors. It is what it is. </span><span style="font-size:16pt">I believe that what matters
to us as programmers, is that our code runs on those devices – <i>that they are
compatible </i>- the topic of this discussion.</span><span style="font-size:16pt"> </span><span style="font-size:16pt"> </span><span style="font-size:16pt">That is to say, I am happy a different path
was not chosen. </span><span style="font-size:16pt"> </span><span style="font-size:16pt">It certainly made my own choices simpler.</span><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">For the record, the main system I run at
home as “<a href="http://ccc.com">ccc.com</a>” happens to be on an Opteron and have no reason to change it. It has a good bit of SCSI storage on it, as well a
number of different types of tapes. It “just works” and OpenBSD runs fine “out of
the box”. The truth is if I changed
it, I’m probably more likely to switch to an unused Tru64 based DS10 with an
Alpha in it than an Intel processor because I have one in the basement that is
currently turned off. However, that
system does not have as many free SCSI channels as the Opteron does and the
OpenBSD box just works. So it remains
with lots of fan, noise and heat, as it is.
</span></p>
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<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">Also, as a computer
scientist, I personally detest the technical aspects of INTEL*64 ISA. For an ISA, I’m unabashedly an Alpha believer.
But the fact is DEC broke from compatibility when the Alpha was
created. And as has been pointed out
Intel/HP did the same with Itanium.
But unlike DEC, which threw everything into Alpha, Intel did not
abandoned x86. Once the team at Intel was realized that IA32 could have a future, the company started to
reinvest. And when Alpha failed in the
market (for whatever reasons), sadly Alpha died.</span></p>
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<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">Which brings be to my primary
point about compatibility. Compatibility
is an economic argument, not a technical one and we often forget that.
I am glad that because Intel decided to stay in (come back too) the main
stream business (IA32) and created INTEL*64 for them to compete, the price was driven
down. As a consumer, I believe that having options is
good. I personally think this is a case where the
market caused the right thing to occur.</span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt"> </span></p>
<p class="MsoNormal" style="font-family:arial,helvetica,sans-serif"><span style="font-size:16pt">‘nuf said – so unless you
want to talk about the compatibility thread, please take it off line.</span></p>
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