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From: bruce@godot.UUCP (Bruce Nemnich)
Newsgroups: net.dcom
Subject: arpanet interfaces -- DH or HDH?
Message-ID: <189@godot.UUCP>
Date: Thu, 11-Oct-84 01:53:18 EDT
Article-I.D.: godot.189
Posted: Thu Oct 11 01:53:18 1984
Date-Received: Fri, 12-Oct-84 05:48:37 EDT
Distribution: net
Organization: Thinking Machines, Cambridge, MA
Lines: 16

I have to decide whether to order a DH or an HDH interface for our 56kb
imp connection.  It seems that the newer HDH interfaces available from
ACC are considerably cheaper than the DH hardware if one includes ECUs
on both ends of the latter.

Is anyone using the ACC HDH interfaces under 4.2?  How compatable are
the two interfaces from the device-driver perspective?  Are there
performance penalties?  How reliable are C/30 HDH connections?

I know of problems at one site (MIT-MULTICS) using an HDH connection;
they claim they had some bugs, but the imp side was not very robust
either, and would routinely mark them "down".  Things are running pretty
well there of late, so the problems may have been fixed.
-- 
--Bruce Nemnich, Thinking Machines Corporation, Cambridge, MA
  {astrovax,cca,harvard,ihnp4,ima,mit-eddie,...}!godot!bruce, BJN@MIT-MC.ARPA