

            basys (3) --- basic computer system simulator            02/23/82


            _U_s_a_g_e

                 basys


            _D_e_s_c_r_i_p_t_i_o_n

                 'Basys'  is  a program designed to simulate a basic computer
                 system configuration  consisting  of  a  central  processing
                 unit,  a disk drive and a central memory.  It is a distribu-
                 tion driven simulator.  In other words, the work load  under
                 which  the  system  is  to  be simulated is characterized by
                 probability distributions  for  such  factors  as  the  time
                 between  job  arrivals, the priority of a job, the amount of
                 memory required by a job, the number of i/o requests  a  job
                 will make, and so on.

                 When  invoked,  'basys'  asks  the  user  for  the following
                 information:

                 -    sssiiimmmuuulllaaatttiiiooonnn llleeennngggttthhh
                      The number of seconds  for  which  the  simulation  run
                      should last is given here.  Note that this is simulated
                      time, not real time.

                 -    mmmeeemmmooorrryyy sssiiizzzeee
                      This  is  the size of main memory in K-words.  All jobs
                      generated by the simulator have memory requirements  in
                      the  range  2K  to  70K  words;  thus,  the memory size
                      specified should probably be greater than or  equal  to
                      70.

                 -    tttiiimmmeee tttooo cccooommmpppaaacccttt mmmeeemmmooorrryyy
                      This  is the amount of time in microseconds required to
                      compress memory to make space available for a job.

                 -    pppeeerrr wwwooorrrddd dddiiissskkk tttrrraaannnsssfffeeerrr tttiiimmmeee
                      This is the time in microseconds required  to  transfer
                      one word between disk and memory.

                 -    dddiiissskkk aaacccccceeessssss tttiiimmmeee
                      This  is  the time in milliseconds required to position
                      the disk head over the desired sector before a transfer
                      takes place.  It includes both seek time and rotational
                      latency.

                 -    iii///ooo ooovvveeerrrhhheeeaaaddd tttiiimmmeee
                      This is the overhead time in microseconds  involved  in
                      the initiation of an i/o request.

                 -    mmmeeeaaannn jjjooobbb iiinnnttteeerrraaarrrrrriiivvvaaalll tttiiimmmeee
                      The  time  in  milliseconds  between  job  arrivals  is
                      generated from an exponential distribution  whose  mean
                      is specified here.




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            basys (3) --- basic computer system simulator            02/23/82


                 -    mmmeeeaaannn cccpppuuu tttiiimmmeee pppeeerrr jjjooobbb
                      The number of milliseconds of cpu time required by each
                      job  is generated from a normal distribution whose mean
                      and standard deviation are specified by this  parameter
                      and the next.

                 -    ssstttaaannndddaaarrrddd dddeeevvviiiaaatttiiiooonnn ooofff cccpppuuu dddiiissstttrrriiibbbuuutttiiiooonnn
                      The standard deviation (in milliseconds) of the per-job
                      cpu time distribution.

                 -    mmmeeeaaannn nnnuuummmbbbeeerrr ooofff iii///ooo rrreeeqqquuueeessstttsss pppeeerrr jjjooobbb
                      The  number  of  i/o  requests  that a job will make is
                      determined by a normal distribution for which the  mean
                      value is specified here.

                 -    ssstttaaannndddaaarrrddd dddeeevvviiiaaatttiiiooonnn ooofff iii///ooo dddiiissstttrrriiibbbuuutttiiiooonnn
                      The  standard  deviation of the distribution from which
                      the per-job number of  i/o  requests  is  generated  is
                      specified here.

                 -    mmmiiinnniiimmmuuummm rrreeecccooorrrddd sssiiizzzeee
                      This  is  the  minimum  number of words in a single i/o
                      transfer.  All transfers  requested  by  a  single  job
                      involve the same number of words.

                 -    mmmaaaxxxiiimmmuuummm rrreeecccooorrrddd sssiiizzzeee
                      The  maximum  number  of  words  in  an i/o transfer is
                      specified here.

                 -    eeevvveeennnttt tttrrraaaccceee
                      If the user responds with "yes", 'basys' will print  on
                      standard  output  two a listing of all pertinent events
                      as they are scheduled and as they occur.  Events traced
                      are job  arrival,  memory  request,  cpu  request,  cpu
                      release,   disk   request,   disk   release   and   job
                      termination.  WARNING:  under reasonable  durations  of
                      simulation,  the  volume  of  output  produced  by this
                      option is prohibitively large.

                 Upon completion of the simulation, 'basys' prints  on  stan-
                 dard  output  one  a three part report.  The first part is a
                 summary of system parameters as specified by the user.   The
                 second part is a table of job descriptions, sorted by ascen-
                 ding job number.  The table gives a profile of each job that
                 entered  the  system  during the simulation run.  Finally, a
                 summary  of  how  well  the  system  performed  is  printed.
                 Included  in  this part are statistics on utilization of the
                 three system resources:  memory, cpu and disk,  as  well  as
                 statistics on the wait queues for each of these resources.


            _E_x_a_m_p_l_e_s

                 parameters> basys
                 basys  >report  >event_trace



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            basys (3) --- basic computer system simulator            02/23/82


            _B_u_g_s

                 Meaningless results accompany meaningless input.

                 Locally supported.





















































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