There's been another batch of moaning from some people wanting to
keep Linux running on Itanium:

https://www.theregister.com/2023/11/21/saving_linux_on_itanium/

My question is _WHY???_ are people still wanting to run Linux on
Itanium for goodness sake ?

Unlike other obscure architectures that Linux runs on, you can't
even emulate Itanium systems in a full-system emulator - you need
the actual expensive, noisy, power-hungry, etc, hardware to run it on.

Huh ???

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.

On 11/21/2023 1:36 PM, Simon Clubley wrote:
> There's been another batch of moaning from some people wanting to
> keep Linux running on Itanium:
>
> https://www.theregister.com/2023/11/21/saving_linux_on_itanium/
>
> My question is _WHY???_ are people still wanting to run Linux on
> Itanium for goodness sake ?
>
> Unlike other obscure architectures that Linux runs on, you can't
> even emulate Itanium systems in a full-system emulator - you need
> the actual expensive, noisy, power-hungry, etc, hardware to run it on.
>
> Huh ???

The commercial interest must be zero. Rare, EOL and expensive
hardware. No software requiring it - I assume there are no software
packages only available for IA-64 and not for x86-64 and
no custom applications written in IA-64 assembler.

But hobbyist interest is different. Hobbyists like stuff
even if it is commercially dead. And some hobbyists like
old hardware as well. There are significant hobbyist
interest for VAX, PDP-11 and PDP-10. Why not for Itanium??

Arne

On Tue, 2023-11-21 at 18:36 +0000, Simon Clubley wrote:
> There's been another batch of moaning from some people wanting to
> keep Linux running on Itanium:
>
> https://www.theregister.com/2023/11/21/saving_linux_on_itanium/
>
> My question is _WHY???_ are people still wanting to run Linux on
> Itanium for goodness sake ?
>
> Unlike other obscure architectures that Linux runs on, you can't
> even emulate Itanium systems in a full-system emulator - you need
> the actual expensive, noisy, power-hungry, etc, hardware to run it
> on.

I suspect it might be just possible to emulate the hardware on today's
machines but one would need their head examined.
--
Tactical Nuclear Kittens

On Tuesday, November 21, 2023 at 3:01:42 PM UTC-8, Single Stage to Orbit wrote:
> On Tue, 2023-11-21 at 18:36 +0000, Simon Clubley wrote:
> > There's been another batch of moaning from some people wanting to
> > keep Linux running on Itanium:
> >
> > https://www.theregister.com/2023/11/21/saving_linux_on_itanium/
> >
> > My question is _WHY???_ are people still wanting to run Linux on
> > Itanium for goodness sake ?
> >
> > Unlike other obscure architectures that Linux runs on, you can't
> > even emulate Itanium systems in a full-system emulator - you need
> > the actual expensive, noisy, power-hungry, etc, hardware to run it
> > on.
> I suspect it might be just possible to emulate the hardware on today's
> machines but one would need their head examined.
> --
> Tactical Nuclear Kittens

You can’t emulate Itanium fast enough in software with any known emulator that’s available to the public and is capable of running the Linux kernel. There’s only a very old partial software emulator called ski.

There’s the even rarer Itanium 1 that people keep around to run the very old canceled Itanium OSs like the SCO/AIX hybrid “Project Monterey” if I’m remembering the YouTube lore. My own HP rx2620 boxes are power-heavy boat anchors that I’d like to sell (1 working dual 2x 1.6 GHz Itanium2 plus 2 more identically configured blades for parts, plus Ultra320 drives + Compaq RAID controller).

You can just barely run OpenVMS and HP-UX on such a system from 2004, and Gentoo Linux at least will run self-hosted with “~ia64” (as with Alpha, only the experimental “~” USE type is supported), but it has nothing to redeem it unless you’re seriously into register windows and “not a thing” bits). I’m surprised the toolchain and the kernel are stable with the default compiler flags in Gentoo. None of the BSDs care about it any more.

The Alpha is more interesting, easier to understand, runs VMS much better, is vastly easier to emulate, and has the distinction of being the production shared-memory SMP architecture that’s the most notorious for the CPUs being allowed to do the most reordering of reads and writes relative to what’s seen from other cores, and doing so.

Consequently, while my Compaq XP1000 and PWS 600au can also just barely run OpenVMS, Tru64 UNIX, and Linux, the EV67 in the XP1000 has the latest and greatest hardware perf counters which Linux “perf” knows about, and the SMP variants of the EV67 and newer would be worthwhile to have in a very thorough Linux kernel or distro CI/CD pipeline if you want to try to catch breakage of read/write dependencies that Alpha requires explicit barriers for.

ARM and most other RISC are somewhere in the middle as far as load and store ordering (and I think Itanium as well?) while x86 and s390x are on the far end of guaranteeing that CPUs see loads and stores in chronological order and many memory barriers convert to nops, which is why it’s nice that the C11 and C++11 stdatomic functions allow you to explicitly state your use of atomic variables so it will hopefully even run on Alpha.

I’m about to test this on my vintage systems with the new local event flag code I finally finished writing for libuv that I can use as a base for converting the socket and eventually other calls from thread pool and poll() to sys$qio and AST callback. I’m getting 12,000 msgs/sec for the async1 benchmark and 18,000 for async2, then it falls back to 12,000 for async 4 and 6,000 for async8, but the results are at least “not crashing” and “not 3k/sec” like I was seeing earlier today.

On Wednesday, November 22, 2023 at 3:43:32 AM UTC-5, John Dallman wrote:
> In article <fac480ada2bcf8d8aa7d32d...@munted.eu>,
> alex....@munted.eu (Single Stage to Orbit) wrote:
>
> > On Tue, 2023-11-21 at 18:36 +0000, Simon Clubley wrote:
> > > Unlike other obscure architectures that Linux runs on, you can't
> > > even emulate Itanium systems in a full-system emulator - you need
> > > the actual expensive, noisy, power-hungry, etc, hardware to run it
> > > on.
> > I suspect it might be just possible to emulate the hardware on
> > today's machines but one would need their head examined.
> It won't happen as a commercial project, because there isn't enough need
> for it to pay back the costs.
>
> Doing it as a hobby or volunteer project is very hard, because of the
> complexity of the architecture, and the lack of people who love it.
>
> Overall, it won't happen.
>
> John

Yep, in one of the recent Dave Cutler interviews, Dave mentioned that whenever a new Itanium chip was released, there was always a faster x86-64 chip already on the market. And since used x86-64 are now available by the boat load (HPE, Cisco, etc), doing such a project could never be justified.

Neil Rieck
Waterloo, Ontario, Canada.
https://neilrieck.net

On 2023-11-22, John Dallman <jgd@cix.co.uk> wrote:
> In article <fac480ada2bcf8d8aa7d32d32cfcd071fe0e0aa4.camel@munted.eu>,
> alex.buell@munted.eu (Single Stage to Orbit) wrote:
>
>> On Tue, 2023-11-21 at 18:36 +0000, Simon Clubley wrote:
>> > Unlike other obscure architectures that Linux runs on, you can't
>> > even emulate Itanium systems in a full-system emulator - you need
>> > the actual expensive, noisy, power-hungry, etc, hardware to run it
>> > on.
>> I suspect it might be just possible to emulate the hardware on
>> today's machines but one would need their head examined.
>
> It won't happen as a commercial project, because there isn't enough need
> for it to pay back the costs.
>
> Doing it as a hobby or volunteer project is very hard, because of the
> complexity of the architecture, and the lack of people who love it.
>

I once spent a few days looking at what was involved in writing an Itanium
full-system emulator and decided I would rather write a browser from the
ground up instead of trying to implement such a thing. :-)

It is a very complex architecture, both in terms of the instruction set
(which is partially addressed by Ski) and the overall full-system design.
In addition, there is information or material (such as the firmware images)
which is not freely available.

The motivation at the time would have been to run a more functional version
of VMS than is possible on Alpha, and that motivation has now been removed
with the introduction, finally, of a viable VMS on x86-64.

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.

On Tue, 2023-11-21 at 17:03 -0800, Jake Hamby (Solid State Jake) wrote:
> > I suspect it might be just possible to emulate the hardware on
> > today's
> > machines but one would need their head examined.
> > --
> > Tactical Nuclear Kittens
>
> You can’t emulate Itanium fast enough in software with any known
> emulator that’s available to the public and is capable of running the
> Linux kernel. There’s only a very old partial software emulator
> called ski.

It's much easier anyway to just install OpenVMS on x86!
--
Tactical Nuclear Kittens

On 2023-11-25, Single Stage to Orbit <alex.buell@munted.eu> wrote:
> On Tue, 2023-11-21 at 17:03 -0800, Jake Hamby (Solid State Jake) wrote:
>> > I suspect it might be just possible to emulate the hardware on
>> > today's
>> > machines but one would need their head examined.
>> > --
>> > Tactical Nuclear Kittens
>>
>> You can?t emulate Itanium fast enough in software with any known
>> emulator that?s available to the public and is capable of running the
>> Linux kernel. There?s only a very old partial software emulator
>> called ski.
>
> It's much easier anyway to just install OpenVMS on x86!

And as mentioned earlier, _that_ removes the last possible reason to
want an Itanium full-system emulator. :-)

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.