🚀 go-pugleaf

gordon@prls.UUCP (Gordon Vickers) writes:

>       I'm considering replacing our VAX 11/750 (Ultrix) with something a bit
>   cheaper to maintain.  Our DEC sales rep. is suggesting a DECstation 3100
>   or the newly announced DECstation 5000.

We replaced our VAX/780 running 4.3BSD with a DECstation 3100 running
Ultrix 2.2.  Since our original computer was a CPU resource, we do not
use the console as an X terminal, which offers more memory for other
applications.

>      Can such a little box really replace a 750 ?  I know technology has
>   come a long way, but still ....... that's an awful small box.

Yes.  Size has nothing to do with speed.  The DS3100 gets about 15 MIPS.
What does a VAX get: 1 MIP.

>      Our 750 seldom has more than four user's but I manage to bog it down
>   with an applications program that runs continously.  This program reads
>   and writes to nine serial ports that communicate over LADS lines at
>   2400 baud to remote equipment. The incoming data occurs in bust of about
>   one kbyte (at random times) , typicaly no more than two ports receiving
>   at a time. We collect about one megabyte of data per day but this will
>   increase to about three megabytes per day within the next two years.

The DECStation is limited to two serial ports, but we bought a terminal
server which then connects to the DS3100 via Ethernet.  All of our users
connect to the terminal server via hard-wired lines or modems, and then 
login to the DS3100.  Also, the terminal server allows connections to our
other systems, and we do not have to provide more wiring.

>      We use two disk drives, an RA80 and an RA81 -Yuck!  We really need
>   something faster and at least slightly more disk space. Something
>   equivilant (in capacity) to two RA81's would work (I don't like the
>   partitioning options of the RA81 either).

We added SCSI CDC Wren VI's to our DS3100 and ran some simple disk
timing programs which showed that the I/O timings were the fourth
fastest in our entire machine room, including SMD drives on SMD
controllers on Sun servers.  Because the DS3100 is fast, it's SCSI
driver is fast, and the new SCSI drives from CDC or Hitachi are very
fast (15-18 ms).  In fact, the new, external drives were faster than
the DEC-supplied internal disk drives.

Also, the cost of the Hitachi 700MB drive was about $2800.  So, for about
$5600 you get 1.5MB of disk space.  Compare this to the cost and size of an
RA80 or 81!

>     The DECstation literature and catalogues I have say nothing about
>   how one adds serial ports.  Are serial devices assumed to be connected
>   via a terminal server or can serial ports be added through an inteligant
>   controller board ?

You can't expand serial ports (I believe); however, why do this when there
are many manufacturers of decent terminal servers which do the job even
better.

>     Can either of these systems realistically support eight simutanious
>   users ?  These are such small boxes, it reminds me of a mulituser
>   PC advertisement I once saw that claimed to support 32 users.  I'm
>   spoilled, I want a computer that waits on me, not visa versa.

Again.  It appears that you are overly concerned with size, and not
performance.  The DS3100 really runs at 15 MIPS, which is *fifteen*
times faster than a VAX/780.  If a VAX/780 could support 8 users, why
can't a machine which runs faster?  Again, size has absolutely nothing
to do with performance.

>     Any followup would be appreciated. I'm not neccessarily looking for
>   a "Yes/No it will do the job" type reply. At this point any information
>   would be welcomed.

The things which you should be concerned with are not the performance
issue, which is quite clear, but the compatibility issue, which is not
at all clear.  There were many applications which we had to port from
the VAX/BSD environment to that of the DS3100/Ultrix system.  This
required time, and, in fact, some ports didn't even work.  For example,
ditroff was never able to port sucessfully (the standard ditroff from
Berkeley).  We had to buy a commercial package to get roff
functionality.

One area which we saved really big was in maintenance.  The cost of
maintaining a VAX/780 was tremendous, and we could buy about two
DS3100's a year just on the savings alone.  This means, really, that we
don't have to get maintenance for the DS3100 -- if it breaks, we buy a
new one, and we're still ahead of the maintenance costs.

Alan Stebbens        <aks@hub.ucsb.edu>             (805) 961-3221
     Center for Computational Sciences and Engineering (CCSE)
          University of California, Santa Barbara (UCSB)
           3111 Engineering I, Santa Barbara, CA 93106

Alan Stebbens <aks@hub.ucsb.edu>