DECconcentrator 500 Operational Firmware V3.4a
                            Release Notes

     This document describes the new  and  changed  functions  of  the
     DECconcentrator 500 Microcode Version 3.4a.

     This  release  of  DECconcentrator  500  firmware  contains   the
     following changes  which  is  new from V3.3.  This formal release
     was deemed manditory because of the perceived implications.

      o  The DEFCN-AC when in  a  dual  homed  configuration  was  not
         indicating proper topology on the led of the port that was in
         standby.

      o  The concentrator was resetting if an OBM disable command  was
         initiated  to  a  nonexistent phy port if a module was in the
         slot.  If no module was present  in  the  slot  that  an  OBM
         disable  phy command was initiated, the returned status would
         correctly indicate the phy port did not exist.

      o  The concentrator would send back an improper  value  for  the
         mib snmpFddiSmtCFState entry.


     Notify the  network  manager  of  the  following  caution  before
     installing the DECconcentrator 500 Microcode Version 3.4a.

      o  Before you download  the  microcode  Version  3.4a  firmware,
         record  all  previously  saved nonvolatile settings.  Restore
         all settings after the downline load is completed.

      o  You must configure the DECconcentrator 500 with an IP address
         using OBM, POLYCENTER Extended LAN Manager (previously called
         DECmcc Extended LAN Manager), POLYCENTER SNMP 300 Version 1.2
         (previously  called DECmcc MSU Version 1.1), or by setting up
         the hardware address of the unit with  an  IP  address  in  a
         BOOTP  server on the network.  Note:  The DECconcentrator 500
         will periodically try to get  its  IP  address  approximately
         every  minute  using the BOOTP until it is configured with an
         IP address.

      o  DECelms does not report the FRU type of the  OBM  UART  card,
         optical-bypass  relay,  or  the six-port ANSI card (DEFCN-H).
         You can use OBM or SNMP (the DEC Vendor MIB) to determine the
         FRU configuration and status of these FRUs.

     The  following tables include current DECconcentrator 500  update
     file device  names  and  locations  after  installation  for each
     operating  system.  DECconcentrator 500 Update Files  for  MS-DOS 
     Systems:

      o  defcn034a, Device name and version number

      o  defcn034a.sys, DECconcentrator 500 image file  found  in  the
         decndu directory


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      o  dc034a.txt,DECconcentrator 500  Version  3.4a  release  notes
         found in the decndu directory

     DECconcentrator 500 Update Files for OpenVMS VAX Systems

      o  defcn034a, Device kit name and version number

      o  defcn034a.sys, DECconcentrator 500 image file that  Open  VMS
         VAX  uses for part of the installation procedure found in the
         MOM$LOAD directory

      o  defcn034a.releasenotes,  DECconcentrator  500  Version   3.4a
         release notes found in the SYS$HELP directory

      o  defcn$ivp.com, Installation verification procedure  found  in
         the SYS$HELP directory

     DECconcentrator 500 Update Files for ULTRIX RISC Systems

      o  FCN034A, Device kit name and version number

      o  defcn034a.sys, DECconcentrator 500  image  file  that  ULTRIX
         RISC uses for part of the installation procedure found in the
         /usr/kits/FCN034A directory

      o  defcn034a.releasenotes,  DECconcentrator  500  Version   3.4a
         release notes found in the /usr/kits/FCN034A directory

     DECconcentrator 500 Update Files for ULTRIX VAX Systems

      o  VCN034A, Device kit name and version number

      o  defcn034a.sys,DECconcentrator 500 image file that ULTRIX  VAX
         uses  for  part  of  the  installation procedure found in the
         /usr/kits/VCN034A directory

      o  defcn034a.releasenotes,  DECconcentrator  500  Version   3.4a
         release notes found in the /usr/kits/VCN034A directory