Shareware Grab Bag/Shareware Grab Bag.iso/007/bufinfo.arc/BUFFERS.TXT

Text File | 1987-03-01 | 6KB | 170 lines

                        Filename:     BUFFERS.TXT
                            Date:     1-Mar-87

               A brief discussion of the DOS buffers command,
                    of particular interest to BBS SysOps

                          Author:     Mike Davidson
                    Organization:     Intermountain Softworks
                                      P. O. Box 2043
                                      Walla Walla, WA 99362







         This document is placed in the PUBLIC DOMAIN.   In that  spirit,
    readers  are  encouraged  to  add substantive comments  on  the  same
    subject.  The suggested form is...

    Name:                                      Subject:
    Organization:                              Date:
    Comment:

    BBS developers and "door"  applications programmers are,  of  course,
    welcome   to  use  any  portion  of  this  file  within   distributed
    documentation.

    Readers are further cordially invited to visit our own PCBoard system
    at 509/529-7229.   Our maximum bit rate is 2400.  We operate 24 hours
    on  weekends,   and  between  1600h  and  0600h  weekdays,   Pacific.
    Weekdays, the system is subject to availability after midnight.







    BUFFERS.TXT - A brief discussion of disk buffers


         Most  operators of computer bulletin board systems are  oriented
    toward the technical.   This is fortunate,  although we have not been
    able to determine if the trait is inherited or a learned necessity.

         In the case of a CONFIG.SYS file which tells DOS to trust  one's
    judgment in a few matters, rather than reverting to defaults, most of
    us  have safely specified FILES to equal some number,  asked that DOS
    install a RAMdisk, and have loaded the ANSI driver.

         The  BUFFERS  command,  however,  may be an  entirely  different
    matter.   To be sure,  the DOS Reference Manual provides a couple  of
    strong hints that a BUFFERS default of two may not be adequate,   but
    hints are often not enough.

         In  our  case,  an even stronger hint came in a message  from  a
    Chicago SysOp.  "What did you do to Tradewars?  It sure is slow!"  At
    the  time,   we  were  still running CPC14.1D of  RBBS-PC,   and  the
    "doorware"   application TRADEWARS was in the RBBS default directory,
    per the author's instructions.   Indeed,  that was the only place  it
    could be.  And that, in retrospect, was a worst-case scenario.

         This  particular  subdirectory  may have had  some  300   files.
    TRADEWARS  was  near  the  bottom of the directory,   and  was  disk-
    intensive,   almost continuously reading from or writing to our  hard
    disk.   This is not to suggest that TW doesn't frequently access  the
    disk  even  under  optimum circumstances,   but  performance  may  be
    substantially improved, as we shall see.

         Moreover,   doorware author Bob Westcott reminds callers,  in  a
    message sent out over the modem,  that return to RBBS may take "20  -
    30  seconds."   And it did.   But Seagate proclaims that our  drive's
    data  transfer  rate  is on the order of five  megabits  per  second!
    Conclusion: BUFFERS!

         Common  sense may suggest that the operating system simply reads
    information  from  a disk and passes it directly to  an  application.
    This is not the case.  An interim holding area, called a disk buffer,
    gets it first.   A disk buffer is a 512-byte block of memory that DOS
    uses  to temporarily hold information it is reading from,  or writing
    to, a disk.










                                   - 2 -






    BUFFERS.TXT - A brief discussion of disk buffers


         If  the buffered data will be used repeatedly,  access time will
    be  improved  significantly if DOS does not have to reread  the  same
    data  each time it is needed.   Users are given the responsibility of
    telling DOS how many 512-byte disk buffers to allocate.  This is done
    within CONFIG.SYS, and uses the syntax...

              BUFFERS = nn

    where nn is an integer between 1 and 99.   Each buffer requested will
    increase the resident size of DOS by 528 bytes.

         Some simple algorithm could doubtless be written to suggest  the
    optimum number of buffers for a particular configuration.   For a 20-
    megabyte  hard disk,  with the number of subdirectories that  PCBoard
    requires,  the magic number,  we believe, is between 15 and 25.   The
    ultimate authority may be a stopwatch.  15 will astound you if you've
    accepted the DOS default of 2;  indeed, PCBoard subdirectory searches
    will appear almost instantaneous.

         As  to  TRADEWARS,  we had occasion to code a short  program  in
    assembler  (CONDORxx.ARC,  available on many PCBoard systems or  from
    us)   for  use with PCBoard 11.7D/E.    CONDOR  thoroughly  convinces
    doorware  applications  they are running under  RBBS-PC.    From  the
    moment   CONDOR   writes  the  RBBS-PC  messages  file,    load   and
    initialization  of TRADEWARS now requires less than five seconds.   A
    miracle?  Hardly.  DOS can do almost anything if given half a chance.
























                                   - 3 -