Subject: Compaq will dump Alpha in favour of IA-64?

From: Shlomi Fish <[email-masked]>
Date: Tue, 26 Jun 2001 11:06:43 +0300 (IDT)

Just spotted this link on Kuro5hin:

http://iwsun4.infoworld.com/articles/hn/xml/01/06/25/010625hnintcomup.xml

What is states is that Compaq will discontinue manufacturing its Alpha
architecture and convert all of its operating systems to the Itanium and
the successor IA-64 chips instead.

This sounds strange considering the fact that Compaq released a document
in which they claimed that Alpha was superior to IA-64 in many ways:

http://www.compaq.com/hpc/ref/ref_alpha_ia64.pdf

This news item smells bad, if you ask me. I heard some very bad things
about the Itanium, and I hate to see an alternative, functional,
architecture getting dumped because of it.

HP will also discontinue its PA-RISC architecture. I wonder what Sun,
SGI and IBM will do.

In any case, is anybody aware of any major differences between all the
common high-end architectures available today? Is there something I can
easily do with architecture X that cannot be done with others, without
implementing a great deal of functionality in software?

BTW, there once was an initiative to have an open-source computer
architecture. It was dubbed the "Freedom CPU" and its homepage can still
be found at http://f-cpu.tux.org/. It seems to be dead as the last news
item is from 1999.

Regards,

	Shlomi Fish

----------------------------------------------------------------------
Shlomi Fish        [email-masked]
Home Page:         http://t2.technion.ac.il/~shlomif/
Home E-mail:       [email-masked]

A more experienced programmer does not make less bugs. He just realizes
what went wrong more quickly.

---

From: Oleg Goldshmidt <[email-masked]>
Date: 26 Jun 2001 11:48:07 +0300

Shlomi Fish <[email-masked]> writes:

> common high-end architectures available today? 

Well, a bit tangential to your question, and focusing on alphas, they
have some interesting quirks. Here are some, my focus being biased
towards intensive computations:

1) no integer division
2) very fast floating point arithmetic
3) in general, computation tends to be preferable to memory access
   (I am not sure if it is all that alpha-specific), so it may be
   preferable to recompute stuff over and over to pre-computing and 
   storing.

There is a very interesting article I came across a few years ago that
discusses optimization techniques on alphas, and gives a brief
not-very-technical overview of alpha chip family and of some
optimization techniques related to the points above. 

http://www.mostang.com/~davidm/papers/expo97/paper/doc000.html

-- 
Oleg Goldshmidt | [email-masked] 
If it ain't broken, it hasn't got enough features yet.

---

From: Adi Stav <[email-masked]>
Date: Tue, 26 Jun 2001 22:28:34 +0300

> HP will also discontinue its PA-RISC architecture. I wonder what Sun,

Intel developed the IA64 with IBM and HP as partners. SGI, too, has been
Intel-committed for a while now, and their big servers are mostly running
IA32. As for Sun, it will drop its UltraSparc when the Devil can overclock
his Itanium by burying it in the snow. It's far too proud (or arrogant,
depends on your point of view). Sun has a large and stable marketshare,
and it has a total control of all the chain of production from CPU through
software to support. It has no reason to change a thing.

> be found at http://f-cpu.tux.org/. It seems to be dead as the last news

I've been tracking this one on and off for several years now. The web site
is rarely updated, but the mailing list was quite alive. I don't know if
it is still the case. I remember they changed their design once or twice.

There are also other similar projects, with varying degrees of progress.
There's Opencores that actually produced some VHDL designs of CPU cores.
And then there's the European Space Agency's complete implementation of a 
Sparc under the GPL (I think).

My own uneducated opinion is that the CPU market, unlike software, is 
too strongly influenced by the competition for the availability of expensive 
fabrication technology and plants to gain much from open designs. Maybe
when Moore's law weakens this will change. Eitan Shefer will probably be
able to tell us more, if he's reading this list.

- Adi Stav

---

From: Shlomi Fish <[email-masked]>
Date: Tue, 26 Jun 2001 12:38:33 +0300 (IDT)

> towards intensive computations:

Are you serious? You mean that Alphas have no integer division? Does a
compiler needs to implement Al-Khuarizmi's Algorithm of Division in
software? (like they used to do for floating-point arithmetics back in the
8088-80386 days).

How bizarre.

Regards,

	Shlomi Fish

> To unsubscribe from this group, send an email to:
> [email-masked]
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

---

From: Oleg Goldshmidt <[email-masked]>
Date: 26 Jun 2001 15:33:50 +0300

Shlomi Fish <[email-masked]> writes:

> Are you serious? You mean that Alphas have no integer division? 

This was in fact my primary reason and justification to send that
follow-up to your query. And I thought it would grab your attention.
;-)

To quote the article I mentioned in that posting,

"The Alpha architecture does not provide an integer division
instruction. The rationale for this is that (a) such operations are
relatively rare and (b) division is fundamentally of an iterative
nature so implementing it in hardware is not all that much faster than
a good software implementation [Alv91]. Nevertheless, there are
important routines that depend on integer division. Hash-tables are a
good example: computing a hash-table index typically involves dividing
by an integer prime constant."

> Does a compiler needs to implement Al-Khuarizmi's Algorithm of
> Division in software? (like they used to do for floating-point
> arithmetics back in the 8088-80386 days).

They still use software to implement floating-point arithmetic on
many platforms. Check the -msoft-float option of gcc.

I actually have a query of my own related to this last point, I'll
ask it in a separate posting, not to mix threads.