





                  A Memory Resident Disk Driver for RSX-11M/M-Plus





          1.0  General


               This distribution kit contains source and command  files  to
          build  a  memory resident pseudodisk for RSX-11M or RSX-11M-Plus.
          The driver builds as a DX:  RX01 floppy disk driver emulator.

               You absolutely MUST have a 22-bit machine in  order  to  use
          this   driver   as   distributed;    this   currently   means   a
          PDP-11/23-Plus, 11/44, 11/70 or 11/74.



          2.0  Building the Driver


               To build the driver, put all the  distribution  files  in  a
          (preferably)  empty UIC and invoke the build command file, SLGEN.
          This build  file  is  quite  intelligent  and  almost  completely
          automatic.   It  should  be able, without manual intervention, to
          build a driver for your system.



          3.0  When Starting Up Your System


               A template command file to install and remove  the  resident
          disk  is provided.  RESDSK.STA is the startup file.  Note that it
          makes use of (M V3.2 and M-Plus V1.0) unsupported features in the
          indirect command file processor to parse and pass a command line.
          RSX-11M users will have to forget about the single  command  line
          feature  unless  the  proper  patches  to BIGIND to support those
          features have been made.

               Please note that RSX-11M systems must have previously  VMRed
          a  RESDSK partition into the system;  RSX-11M-Plus loads the disk
          partition in GEN, on the high end.   If  you  have  other  things
          which  go  in the high end of GEN, the resident disk and its data
          partition must be loaded first.



          4.0  If Your System Already Supports a DX: Driver


               If your system  already  supports  a  DX:   driver,  certain
          changes  in in the data base, file names, and the command file to
          reflect a different driver  name  must  be  made.   This  is  not


                                                                     PAGE 2



          difficult.   As  most  systems  do  not support both DX:  and DY:
          devices, a good alternate name for this "device" might be DY:.



          5.0  Caveat, RSX-11M Users


               Conditionalization of the data base  for  RSX-11M  has  been
          done,  but no guarantee is made that this driver works on RSX-11M
          systems.  This is particularly true on systems with less than 128
          K, because this disk builds for a 512 block (128 K) disk.



          6.0  Problems, Suggestions, Further Information


               For those who may  be  interested,  a  formal  treatment  of
          theory  and implementation of memory resident disks will be found
          in the Proceedings of the Fall 1982 DECUS Symposium.

               If you have problems or suggestions regarding  this  driver,
          please submit them - in writing with pertinent documentation - to
          the author at the  address  below.   Phone  calls  and  in-person
          visits regarding this package will be politely refused.



                                   Bruce R. Mitchell
                                   3M Engineering Systems and Technology
                                   Building 518-1
                                   3M Center
                                   St. Paul, Minnesota
                                   55144

