GNP DEI-1 Port Mux (Rev

[Robert Nagler]

This is a review of a port multiplexer from GNP Computers in Pasadena, CA
(818-577-4252).

The DEI-1 port multiplexer is an S-Bus board and external mux box with a
separate power supply.  You can see the advertisement in SunExpert and
probably SunTech as well.  The mux box has 4 slots.  Each slot holds a
board with 8 RS232 asynch and 1 parallel port.  They are apparently coming
out with an X.25/synchronous card and a modem card, that is, you'll be
able to mix various boards in one mux box.  The S-Bus card gets the
majority of its software from the Sun--no PROM upgrades unless the
download protocol changes.

We currently use ALM-1s attached to Sun3/280s (SunOS 3.2 :-) which are
connected to customer workstations (386s, DECs, SUNs) via RS232 9.6k and
2.4k lines.  The serial traffic varies from light to intense in both
directions.  A 3/180 (haven't tested this with our 3/280s) can easily be
overloaded with only 14 clients distributed over 32 lines (2 ALM-1s).  We
use a homebrew asynch packet protocol implemented in user code which you
can think of as a UDP router.

We loaded a DEI-1 with 8 ports (not tough enough, but we only have 8
ports) on a SS1+ (SunOS 4.1) with 32MB (no paging).  Each port was
connected to a 386 running our router software and a postscript display
engine.  The SS1+ ran 8 driver applications and 8 routers.  It was also
running SunView and load monitoring software.  Each port was loaded to the
degree that would make a 3/180 sluggish.

The load average hardly went above 0.1 and SunView was quite lively (as
lively as it gets).  Occaisionally, there would be a couple of tenths of
second delay on character echoes.  After adding a CPU bound task, the load
increased to 1, but SunView was still happy.  We added another driver
application which transfers data continuously over the ports.  This
brought the load up to 3, but these processes were mostly waiting on I/O
so SunView was reasonable (1 to 2 sec echo delays at times). 

We are confident that the SS1+/DEI-1 can handle all 32 ports.  We haven't
tested the parallel port.  The GNP people have been quite helpful by
sending us free driver updates via e-mail--in Europe this matters.
Obviously our test was extremely subjective, but we are a small shop.  We
didn't try other boards, because they didn't support 32 ports without
eating many S-Bus slots.  (We know about Uninet SLAT box, but they
promised an extensible box which they don't have.)  We are planning on
using IPCs for production servers so slots are an issue.

Disclaimer: I'm just a satisfied customer, no other connection with GNP.

Rob nagler at olsen.uu.ch