TOPS-20 Beware File

                           Version 7(21017)

                       Last Revision: 01 Jun 88





     COPYRIGHT (C) DIGITAL EQUIPMENT CORPORATION  1976,  1987,  1988.   ALL 
     RIGHTS RESERVED.

     THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY BE USED AND  COPIED
     ONLY  IN  ACCORDANCE  WITH  THE  TERMS  OF  SUCH  LICENSE AND WITH THE
     INCLUSION OF THE ABOVE COPYRIGHT NOTICE.  THIS SOFTWARE OR  ANY  OTHER
     COPIES  THEREOF MAY NOT BE PROVIDED OR OTHERWISE MADE AVAILABLE TO ANY
     OTHER PERSON.  NO TITLE TO AND OWNERSHIP OF  THE  SOFTWARE  IS  HEREBY
     TRANSFERRED.

     THE INFORMATION IN THIS SOFTWARE IS SUBJECT TO CHANGE  WITHOUT  NOTICE
     AND  SHOULD  NOT  BE  CONSTRUED  AS  A COMMITMENT BY DIGITAL EQUIPMENT
     CORPORATION.

     DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE OR  RELIABILITY  OF  ITS
     SOFTWARE ON EQUIPMENT WHICH IS NOT SUPPLIED BY DIGITAL.

TOPS-20 Beware File - Version 7(21017)                          Page 2


                          TABLE OF CONTENTS


        1.0     FUNCTION OF THIS DOCUMENT  . . . . . . . . . . . . . 3
        2.0     CRITICAL CAUTIONS AND CORRECTIONS (READ THESE 
                CAREFULLY) . . . . . . . . . . . . . . . . . . . . . 3
        2.1       New KL Microcode . . . . . . . . . . . . . . . . . 3
        2.2       DFCIA Use With Login Structures  . . . . . . . . . 3
        2.3       Edit 7449 And SKDCL1 BUGHLTs . . . . . . . . . . . 3
        2.4       Job 0 Forks  . . . . . . . . . . . . . . . . . . . 3
        3.0     LESS CRITICAL PROBLEMS . . . . . . . . . . . . . . . 4
        3.1       New System Logical Names . . . . . . . . . . . . . 4
        3.2       INFO% JSYS   . . . . . . . . . . . . . . . . . . . 4
        3.3       Canceling Requests . . . . . . . . . . . . . . . . 4
        3.4       The Old Mailers  . . . . . . . . . . . . . . . . . 4
        3.5       Dump-on-BUGCHK Timing  . . . . . . . . . . . . . . 5

TOPS-20 Beware File - Version 7(21017)                          Page 3
FUNCTION OF THIS DOCUMENT                                    01 Jun 88


     1.0  FUNCTION OF THIS DOCUMENT

          This document supplements the TOPS-20  manuals  by  pointing
     out hints and potential problems discovered at the last minute.



     2.0  CRITICAL CAUTIONS AND CORRECTIONS (READ THESE CAREFULLY)

     2.1  New KL Microcode

          Version 7.0  of  TOPS-20  uses  the  new  PMOVE  and  PMOVEM
     instructions.   These  instructions  were  made  available  in KL
     microcode version 2.1(442).  This microcode version  is  required
     for TOPS-20 version 7.0.



     2.2  DFCIA Use With Login Structures

          DFCIA can no longer be run under  TOPS-20  if  that  TOPS-20
     system  has a Login Structure that is on an RA81 or a dual ported
     disk.  This is because you need  to  dismount  all  CI-accessible
     structures  and OPR>SET PORT CI UNAVAILABLE to run DFCIA, but you
     can't dismount the Login Structure.



     2.3  Edit 7449 And SKDCL1 BUGHLTs

          It was discovered that edit 7449 had adverse side-effects on
     the  loading  of DN60s.  This edit was intended to prevent SKDCL1
     BUGHLTs which can occur after  a  powerfail  restart  during  the
     loading  of the DN60.  This edit was removed and the problem will
     be addressed differently in a  future  Autopatch  tape.   In  the
     interim,  be aware that these BUGHLTs may reappear.  We are sorry
     for any inconvenience that this may cause.



     2.4  Job 0 Forks

          It is strongly suggested that the GALAXY processes run under
     their  own  job and be under the control of PTYCON.  Also, NEBULA
     should be run in a separate job as it  uses  many  sub-forks  for
     DECnet  communication.   Provided  in  the  first  saveset on the
     Installation tape are sample 7-SYSJOB.RUN and 7-PTYCON.ATO  files
     which  can  be  used  as guides in setting up a more flexible and
     efficient arrangement for the important system forks.

TOPS-20 Beware File - Version 7(21017)                          Page 4
LESS CRITICAL PROBLEMS                                       01 Jun 88


     3.0  LESS CRITICAL PROBLEMS

     3.1  New System Logical Names

          The Login Structure feature introduces new logical names  to
     the  system.   At  startup,  the  following new logical names are
     defined:


      o  BS:  => Points to the swapping structure (PS:  unless using a
         Login Structure)

      o  SERR:  => BS:<SYSTEM-ERROR>

      o  SPOOL:  => BS:<SPOOL>

      o  TGHA-DATA:  => BS:<SYSTEM>


          If any of these logical names are  changed,  programs  which
     use them (including GALAXY, TGHA, ACTGEN, SETSPD, CHKPNT, and the
     monitor) could fail  to  work  properly.   Also,  as  of  TOPS-20
     version  7.0,  there cannot be a structure called BS:  as this is
     assumed to be the swapping structure.



     3.2  INFO% JSYS

          When using the INFO% JSYS, argument blocks  for  information
     to be returned cannot be in ACs 1-4.  The reason is because INFO%
     preserves user's T1-T4 because it uses them at will  during  JSYS
     call simulation.



     3.3  Canceling Requests

          A privileged user can no longer just give the request number
     of  a  request to cancel if that request is not his.  He must now
     also specify the /USER:  switch.



     3.4  The Old Mailers

          The old  TOPS-20  mail  system  (MAIL/MAILER/RDMAIL)  is  no
     longer  supported.   These programs have been placed on the tools
     tape along with the old ARMAIL.MAC  (renamed  MAILER-ARMAIL.MAC).
     The supported mail system, MS/MX, has replaced MAIL/MAILER/RDMAIL
     and  the  supported  ARMAIL.MAC   will   communicate   with   MX.
     Therefore,  any  programs  which  use  ARMAIL, such as the GALAXY
     subsystem, will also communicate with MX.

TOPS-20 Beware File - Version 7(21017)                          Page 5
Dump-on-BUGCHK Timing                                        01 Jun 88


     3.5  Dump-on-BUGCHK Timing

          The Dump-on-BUGCHK  (DOB)  facility  turns  off  timesharing
     while  the  system is being dumped.  If the DOB takes an extended
     period of time, LAT and/or DECnet and/or Arpanet connections  may
     be  lost.   Therefore the fastest available device should be used
     for DOB dumps.  A couple of example memory dumping times follow.

             Device          Memory size     DOB time
             ------          -----------     ----------
             RP07            1.5 Mw           6 seconds
             RP07            4.0 Mw          16 seconds
             RP06            1.5 Mw          11 seconds
             RP06            4.0 Mw          32 seconds
             RA60/81         1.5 Mw          21 seconds
             RA60/81         4.0 Mw          56 seconds