     This directory contains a modified version of Stamerjohn's
     famous 11m virtual disk driver package. 

     Herein  is  a  version of AVD which allows one to assign a
     virtual disk by specifying the starting block  number  and
     the  extent.  We  use  this  along  with our AED-8000 disk
     controller to simulate an rp06 with 1200 or  so  cylinders
     (rp06  has  only  about 800). Thus The first 2/3rds of our
     disk appears to rsx as an exact replica of  the  rp06  and
     the  last  third  (accessable  by  patching the ucb of the
     driver to permit 515000 blocks) is a virtual disk. Thus we
     can hardware boot it without making any  patches  to  boot
     and  sav as well as we can use preserve on the first 2/3's
     (we never backup the  virtual  disk  -  use  it  just  for
     scratch). 

     One  other  possibility  is to assign a virtual disk which
     overlaps the actual disk BUT AS  READ-ONLY.  We  use  this
     whenever we use BRU (after it wiped us out one time). Also
     one  can  then  read  any where on the disk one wants (say
     with dump) to look at the boot block etc. - all  with  the
     disk up and running for other users. 

     Of  course  you need the Virtual disk package from earlier
     decus tapes. If you are not familiar with the virtual disk
     driver I recommend you look into it. It is one of the most
     useful programs (especially for its size) that I have come
     across on the tapes. (When I asked Dec why  they  wouldn't
     support  it they said: 'We intend to write one ourselves',
     but I doubt if it will ever be as good.) 
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
;	MCR COMMAND LINE IN FORM SHOWN BELOW.
;
;               avl VDN:=/SW
;
;		VDN:	VIRTUAL DISK TO ASSIGN.
;               /SW     SWITCHES:
;
;                       /RO     ALLOW ONLY READ ACCESS (optional)
;                       /be:beginblock  (necessary)
;                       /si:size        (necessary)
;
; OUTPUT:
;
;       VIRTUAL DISK ASSIGNED TO area on disk  OR ERROR MESSAGE
;	OUTPUT TO USER'S TERMINAL.
;
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
