[Info-vax] DEC Multia (UDB) issues

[Hans Vlems]

On Aug 27, 2:28 pm, John Wallace <johnwalla... at yahoo.co.uk> wrote:
> On Aug 27, 10:16 am, Hans Vlems <hvl... at freenet.de> wrote:
>
>
>
>
>
> > On Aug 26, 10:42 am, John Wallace <johnwalla... at yahoo.co.uk> wrote:
>
> > > On Aug 26, 9:11 am, Hans Vlems <hvl... at freenet.de> wrote:
>
> > > > On Aug 23, 1:26 pm, MG <marcog... at SPAMxs4all.nl> wrote:
>
> > > > > On 23-8-2011 12:39, Hans Vlems wrote:
>
> > > > > > Running VMS on a Multia is not that difficult, even I managed to make
> > > > > > it work. My Multia came with just 40 MB main memory IIRC and though
> > > > > > VMS will boot and run in that limited space it halted within half an
> > > > > > hour.
>
> > > > > Which version did you run, do you recall that?
>
> > > > VMS V7.3.
>
> > > > > I'm a bit surprised, to be honest, that VMS wouldn't be able to handle
> > > > > that.  Is it as simple that Alpha, being 64-bit, would ordinarily
> > > > > require more RAM?  Or were you performing complex calculations, heavily
> > > > > using DECwindows and therein based programs, perhaps?
>
> > > > The 40 MB came in four boards: two 12 MB boards and two 8 MB boards.
> > > > My conclusion after a
> > > > couple of sudden stops of VMS (and that doesn't happen too often,
> > > > right) was that either 40 MB was
> > > > not enough to run X-motif in or perhaps that one of the memory boards
> > > > was slowly going south.
> > > > Then I learnt that AlphaServer 1000A boards fit in a Multia and after
> > > > the memory upgrade the problems were over.
> > > > So the cause is still uncertain.
> > > > BTW a Multia is slow compared to an AlphaServer 300 4/266 system which
> > > > has about the same internals.
>
> > > > > I'm asking because most VAXen with even less memory will run just fine,
> > > > > I've noticed (like some of the IPv7.net nodes).
>
> > > > Correct but the memory requirements of 32 bit VMS and 64 bit VMS are
> > > > quite different. Furthermore Alpha/VMS has
> > > > functionality in it that just is not present in VAX/VMS. And VAX/VMS
> > > > started life on a VAX 11/780 where memory capacity
> > > > could be as low as 256 kB (entry level 128 kB perhaps!).
>
> > > > > > The memory was expanded to 256 MB with memory boards with a height that
> > > > > > only just fitted with the box closed. Well, you read about its cooling/
> > > > > > airflow issues so the memory was reduced to 4 x 32 MB boards. It shares
> > > > > > memory boards with the AlphaServer 1000A 5/xxx models.
>
> > > > > There's a mere 32 MB in mine.  I don't think I really want to use the
> > > > > system for anything else than a glorified DECterm (especially since my
> > > > > LK463 works fine on it) to connect to my I64 cluster.  32 MB should be
> > > > > fine for that, correct?
>
> > > > Very likely, my Multia ran the DCE desktop on the graphics console and
> > > > at the same time I ran an X-session on
> > > > a PC with Reflection installed. And Motif is possibly not the easiest
> > > > windows environment...
> > > > If you just run the old style DECwindows kit, like the one that runs
> > > > on top of VAX/VMS then 32 MB will work.
> > > > Though adding memory is cheap (eBay) and any upgrade from 32 MB will
> > > > be noticable.
>
> > > > > > This works well, though its built in 10 Mb/s ethernet adapter slows it
>
> > > > > Purely out of curiosity, since you brought this up: Are 100BASE-TX
> > > > > ethernet adapters, since there's one PCI slot, available/known to work
> > > > > in it?
>
> > > > I have never dared to try! The Multia has cooling issues and I didn't
> > > > want to install too much additional equipment in it.
> > > > I also have an AlphaServer 300 which outperforms the Multia, so once
> > > > VMS was installed I lost interest in the Multia.
> > > > My study in the attic is small, has no airco and is fairly warm from
> > > > april to september. So not an environment to keep a
> > > > Multia in for daily work (a Digital Server 5305 does just that now).
> > > > AFAIK there are no restrictions on what you can put on the Multia's
> > > > PCI bus. A DE500 interface ought to work and wouldn't
> > > > raise the inside temperature too much. YMMV.
>
> > > > >   - MG
>
> > > > Hans
>
> > > "a Multia is slow compared to an AlphaServer 300 4/266 system which
> > > has about the same internals. "
>
> > > A Multia is indeed slow, but there are no other mainstream Alpha boxes
> > > with "about the same internals" because there are no other boxes based
> > > on the 21066/21068 CPU chip family used in Multia. The AlphaBook is
> > > close though (and there were VME boards but that's a different story).
>
> > > It's the 21066/21068 that is the main performance constraint in the
> > > Multia, not what's around it, although having enough memory is
> > > obviously important too.
>
> > > The 21066/21068 has pretty much everything integrated onto the CPU
> > > chip itself, apart from the SIMMs and the graphics and  and a handful
> > > of PCI-derived IO (the PCI bus comes direct off the 21066/21068).
> > > There is no off-chip northbridge/southbridge equivalent as used on
> > > 21064, x86, etc. The 21066/21068 is not quite an ARM-licencee-style
> > > "system on chip" but it's a lot closer than an x86 or other Alpha
> > > design would be.
>
> > > Getting an x86-based Multia into the same form factor later in the
> > > life of Multia was quite an achievement in its day, given all the x86
> > > support electronics needed.- Hide quoted text -
>
> > > - Show quoted text -
>
> > The Multia does indeed run at a lower clock speed, 12% slower than the
> > AS300.
> > I'd forgotten about that. Another cause for a poorer performance is
> > the 2,5" notebook
> > harddisk.
> > For its time the Multia was a marvel, lots of power in a very small
> > box, not unlike the
> > release of the VAXstation 2000. The latter has less heat issues and a
> > more rugged
> > construction quality, though.
> > Hans
>
> $ SET MODE /PEDANT
>
> The clock speed difference tells only part of the performance story.
> There are a number of other relevant differences between the
> 21066/21068 chip in the Multia and the 21064(A) chips and chipsets in
> other Alphas of the era, including
> . on chip cache size and effectiveness
> . off chip cache size and effectiveness
> . system bus width to main memory (64 bits on Multia, 64 or 128
> depending on model with other Alphas)
> . system bus performance in other respects (e.g. Multia uses CPU->memory bus cycles to do DRAM refresh)
>
> . PCI bus performance
>
> The marvel isn't just the Multia, it's based on everything that was
> incorporated in the 21066/21068 chips (to reduce the overall system
> cost). But the reduced system complexity and cost came at a price;
> performance took a hit.
>
> A quick dig around for price and performance numbers found these 1995
> examples [1] (which I haven't verified but it sounds plausible):
>
> Same clock speed, different processors, little config info:
>
>      processor       SPECint92       SPECfp92
>         21066-233       94              110
>         21064a-233      157             183
>
> Slightly different clock speeds, different processors, a bit of config
> info:
>
> Type     Speed   Cache   Processor       Price   SPECint/SPECfp
> AXPpci33 233MHz  256kb   21066           $1,395    94 / 110
>
> PC64     275MHz  2MB     21064a          $4,295    189 / 262
>
> Summary: Clock speed alone is not a reliable predictor of performance.
>
> [1] figures found in two separate posts in a
> comp.os.linux.development.system thread titled "Linux on a DEC Alpha"
> starting on Sep 5 1995, find it athttp://groups.google.com/group/comp.os.linux.development.system/brows...
> or wherever
> but probably sourced originally from DEC data which wasn't so easy to
> find.- Hide quoted text -
>
> - Show quoted text -

HI John,
clockticks per second is not the only performance indicator. The rest
of the motherboard design
is also a very important. When comparing systems the most important
issues in performance as
seen by the enduser are processor speed, available memory and disk
subsystem performance.
The slow 2,5" SCSI disk in the Multia sure doesn't help either.
What bugs me most about the Multia is it tendency to crash, ambient
temperatures last weekend
were high (for the Netherlands), say 25 Celsius indoors. Could that
have caused the system to
overheat?
Hans