CP/M/CPM_CDROM.iso/cpm/misc/fast2.ark/FAST.MAN

Text File | 1983-09-09 | 18KB | 511 lines

         WHAT IS FAST AND HOW DOES IT WORK?


What is FAST?  It is  a new  transient program  for the CP/M
(*) disk operating system.  FAST is used in conjunction with
other transients  to speed  up their  execution.  Of course,
nothing but a hardware change can increase the rate at which
your CPU executes  instructions.  But,  most  transients are
"disk bound", that  is,  they  spend  a  large percentage of
their total execution time just  waiting for the information
they need from  the disk.  FAST  uses this  fact to increase
execution speed by reducing  the time spent  waiting for the
disks.  This is accomplished by using two different types of
buffering.  Firstly, portions   of   the   disk   which  are
frequently accessed (the  directory) are  held in  a buffer,
eliminating the need  to seek to  read them.  Secondly, disk
accesses are grouped together  in time to  reduce the amount
of time lost to rotational latency and head load delay.


               HOW TO USE FAST


The normal CP/M  command to  assemble a  file with  the name
MUMBLE.ASM is:

    A>ASM MUMBLE

To perform the same function under FAST, simply type:

    A>FAST ASM MUMBLE

Thus, in its simplest form, FAST can  be used as a prefix to
any normal CP/M  command.  This  will  load  FAST which will
link itself to your  operating system and  allocate its disk
buffers.  Then the transient  ASM.COM  is  loaded  and given
control.  The fact  that FAST  is in  the system  is totally
transparent to the transient, except  for the reduced memory
size.  Messages will be  printed just  before and  after the
transient is executed to  indicate that FAST  is in control.
After execution, you should see  something like this on your
terminal:

    A>FAST ASM MUMBLE
    Beginning execution under FAST N.NN
    CP/M ASSEMBLER - VER 1.4
    1234
    056H USE FACTOR
    END OF ASSEMBLY
    Execution under FAST now complete
    A>

Where N.NN is the version number of FAST that you are using.










FAST Users Manual    5/29/79                Page 2
Command line options

            COMMAND LINE OPTIONS


The buffering action of FAST may  be altered with the use of
command line options.  This is accomplished by following the
FAST command  with  an  option  string  enclosed  in  square
brackets ("[" and "]").  A valid  option string must consist
of a drive specification  followed by one  or more buffering
mode  specifications.  This  group   may  be   repeated  for
buffering of multiple  drives.  Examples  of  typical option
strings will be given below.


Explicitly specifying the  buffering  mode  is  desirable to
reach the best  trade-off  between  speed  of  execution and
memory  usage.  In  general,  as  more  buffering  is  used,
execution  speed  will  increase.  However,  more  buffering
means more memory  usage.  The  type  of  buffering selected
should be  tailored  to  the  disk  usage  patterns  of  the
transient being  executed.  For  instance,  write  buffering
will offer no speed improvement  when a transient only reads
the disk.


One thing that FAST must  know is which disk  drive is to be
buffered.  This is communicated to FAST  simply by using the
single letter name of the  desired drive (e.g.  "A" for disk
drive A).  As a  convenience, the current  default drive may
be specified with the commercial at sign ("@").


The second thing  which  FAST  must  know  is  which mode of
buffering is  to  be  used.  FAST  supports  three different
buffering modes.  Each mode  may be used  individually or in
combination with other modes to offer the fastest execution.
The three modes available are:

     Seek buffering
     Read buffering
     Write buffering
     Yes (all of the above)

The type of buffering  desired is communicated  to FAST by a
single letter in  the option  string.  The letter  is simply
the first letter  of the  word which  describes the  type of
buffering   (capitalized    above).  The    operation    and
application of each mode will be discussed below.


Thus, a typical FAST command line might look like this:

    B>FAST [ASWBSR] ASM MUMBLE.BAA

In this example, the .ASM source file  is on drive B so read
and seek buffering have been  specified for that drive.  The
A drive, on the other hand, is  to receive the result of the
assembly (the .HEX  and .PRN  files), so  it gets  write and
seek buffering.





FAST Users Manual    5/29/79                Page 3
Command line options

         BUFFERING MODE DESCRIPTIONS


Seek buffering causes the  disk directory to  be read into a
buffer the first  time a  drive is  accessed.  From then on,
all reads from and  writes to  the directory  can be carried
out without moving the disk  head from its current position.
Thus, transients which access  the directory frequently will
be sped up considerably by seek buffering.  Transients which
fall into this  category  are  those  which  deal  with many
different  files  simultaneously,  perform  operations  with
temporary files and rename  them, read or  write large (more
than 16K) files,  and those  which perform  random disk I/O.
In particular, ASM.COM,  MAC.COM,  PIP.COM,  and  ED.COM are
examples of such transients.


Read buffering causes an  entire track  from the  disk to be
read into a  buffer the first  time any sector  is read from
that track.  This  increases  execution  speed  because CP/M
typically reads most  of one  track before  going on  to the
next one.  Additionally, the  time required to  read a whole
track is a  fairly small  percentage increase  over the time
required to read  a single  sector.  The net  effect is that
less time is spent waiting for the rotational latency of the
disk.  This  mode  of   buffering  is   most  beneficial  to
transients which read disk  files sequentially.  As a matter
of fact, it may  slow down transients which  read files in a
random access mode.  Fortunatlly, the  vast majority of CP/M
transients read  the  disk  sequentially.  Examples  of such
transients are ASM.COM,  MAC.COM,  PIP.COM,  and BASIC-E.COM
(if the BASIC program doesn't do random I/O!!).


With write buffering, sectors that are to be written to disk
are held in  a buffer  for a  time, instead  of writing them
immediately.  Sectors for any  given track  are held  in the
buffer until  CP/M tries  to write  to a  track that  is not
buffered.  When it is  time  to  change  tracks,  only those
sectors which  were  changed  are  actually  written  before
clearing the buffers  to make  room for  the new data.  This
improves execution speed  for  the  same  reasons  that read
buffering does, i.e. a  whole track can  be written in about
the time it  takes  to  write  a  single sector.  Transients
which benifit from this type of buffering typically write to
disk sequentially.  Examples  include ASM.COM,  MAC.COM, and
ED.COM.


             DEFAULT PHILOSOPHY


Two of  the  qualities  generally  associated  with  a  good
program are versatility  and  ease  of  use.  FAST  has been
written with these  two  qualities  in  mind  as the primary
design goals.  Many times,  however, these two  goals can be
contradictory.  A versatile program is  one which is capable
of a wide variety  of tasks or one  that fits many different





FAST Users Manual    5/29/79                Page 4
Default philosophy

applications.  This usually means  a program  with many user
selectable options.  Forcing  the  user  to  type  the  same
frequently used options every  time a program  is invoked or
committing him  to  remember  a  long  list  of  options  is
contradictory to the goal of  ease of use.  This conflict is
resolved by the use of default mechanisms within FAST.


A default mechanism  is simply  a rule  that can  be used to
make assumptions  about the  user's wishes  when he  has not
stated them explicitly.  Thus, versatility has been retained
by  allowing  the  user  the   ability  to  specify  options
explicitly, while the default mechanism  frees the user from
this tedium much  of  the  time.  In  short,  defaults allow
versatility and ease  of use  to peacefully  co-exist in the
same program.


         DEFAULT MECHANISMS IN FAST


There are two levels of defaults built into FAST.  The first
default mechanism is used when either the drive or buffering
mode is omitted from  an option string.  If  a drive name is
not given, the  default  drive  for  CP/M  is  used (this is
equivalent to "@").  If no buffering mode is specified, read
and  seek  buffering  are  used.  Thus,  the  following  two
commands would be equivalent.

    B>FAST [BRW] LOAD MUMBLE

    B>FAST [RW] LOAD MUMBLE

And so would the following two commands.

    A>FAST [BRS] PIP B:THIS=B:THAT

    A>FAST [B] PIP B:THIS=B:THAT


The second default mechanism comes  into play when no option
string is given  on the command  line.  Instead of executing
the transient with no buffering,  FAST uses a default option
string to specify the buffering used.  This string is [@RS],
giving the user read and seek buffering on the default drive
when no option string  is present on  the command line.  The
user may, at  his option,  alter the  default option  to one
which is more suitable for  his typical uses.  For instance,
if you typically use  FAST for assembling  and don't have to
worry about  running out  of memory,  a good  default string
would be [@RWS].  Conversely, if you  are running in a small
memory system, a good choice would be [@R].











FAST Users Manual    5/29/79                   Page 5
How to change the default option string

       HOW TO CHANGE THE DEFAULT OPTION STRING


The default string  is  stored  in  FAST  at  address 0130H.
Thus, to change the option string,  use SID or DDT to change
the existing string.  Assuming  you  have  SID  this is very
easy:

    A>SID FAST.COM
    SID VERS 1.4
    NEXT  PC  END
    0900 0100 94FF
    #S130
    0130 5B "[@RWS]
    0136 20 .
    #^C
    A>SAVE 8 FASTX.COM

If you do not  have SID, you'll  have to use  DDT and figure
out the hex for the ASCII string you wish to patch in.  Then
use the Substitute command  to patch the  file as above.  In
either case, test  the patched  file before  killing the old
FAST.COM and renaming the new file to FAST.COM.


              WARNINGS


N-E-V-E-R CHANGE DISKS WHILE EXECUTING UNDER FAST!!!

Wait until  you see  the message  "Execution under  FAST now
complete" before switching disks.


A rather nasty side  effect  of  seek  buffering  is that it
disables the disk change detection mechanism built into CP/M
version 1.4.  This means that you can't expect the operating
system to give the  warning message BDOS ERROR  ON A: R/O if
you forget and change disks without booting.


This also  gives rise  to a  minor incompatibility  with any
transients which use the BDOS reset function (BDOS call 13).
This function is used in transients  which allow the user to
change disks without rebooting.  The only transient which we
are currently  aware  of  which  fits  this  description  is
Microsoft's MBASIC.COM.  MBASIC uses this BDOS function only
when the RESET  command  is  used.  FAST  is compatible with
MBASIC as long as the RESET command is not used.


A good rule  to  remember  is  never  to  use  FAST with any
transient which requires user input.  Any such transient, by
waiting for your reply, would leave you with the opportunity
to change disks.








FAST Users Manual    5/29/79               Page 6
Warnings

            COMPATIBILITY


FAST is fully  compatible with the  following transients and
can be  expected  to  provide  a  significant  reduction  in
execution time.

     ASM       LOAD      SUBMIT    DUMP      MAC
     TEX       COMPARE   MODEM     FILES     PRINT
     COMBINE   UNLOAD    FROMISIS  TOISIS    ICOPY
     IDIR


FAST is fully compatible with  the following transients, but
due to fact  that  they  require  user  input,  some caution
should be  exercised  when  they  are  used  with  FAST.  As
mentioned above,  stopping  for  input  gives  the  user the
chance to inadvertently change disks which CP/M would not be
able to detect.  If the  user is able  to guard against this
occurrence, he may use FAST with these transients and expect
a significant reduction in execution time.

    ED       PIP         DDT    SID       MBASIC
    XYBASIC   BASIC-E   RUN    WORDMASTER


FAST is fully compatible with  the following transients, but
due to the way  in  which  they  access  the  disk, no speed
improvement can be expected.

     SYSGEN        MOVCPM        FAST


Due to an unfortunate memory  dependency, STAT (version 1.4)
does not correctly report  the number of  bytes remaining on
the disk when it  is executed under  FAST.  This is no great
loss because FAST can do little to speed up the execution of
STAT.


            FAST MESSAGES


During the  course  of  execution,  FAST  may  print  any of
several  different  messages.  Each  of  these  messages  is
listed  below  along  with  conditions  under  which  it  is
printed.

Beginning execution under FAST N.NN
     This message  is  printed  after  the  transient  to be
     executed under fast  has been  successfully loaded, but
     just before  control  is  transfered  to  it.  This  is
     simply an informatory  message and  does not  signal an
     error condition.  In this message,  N.NN is the version
     number of FAST which you are using.








FAST Users Manual    5/29/79                Page 7
FAST messages

Execution under FAST now complete
     This  message  is  printed   after  the  transient  has
     finished execution  and  all  disk  buffers  have  been
     emptied.  This too  is  simply  an  informatory message
     printed under normal conditons.

NO COM FILE
     This message is  printed  when  the  transient filename
     given on  the  command  line  cannot  be  found  in the
     directory.  No recovery action  can  be  taken,  so the
     execution complete   message   is   printed   and  FAST
     re-boots.

OUT OF MEMORY
     This message is  printed when  the size  of the  TPA is
     exceeded while allocating buffers  or while loading the
     transient.  In either case,  no recovery  action can be
     taken, so the execution complete message is printed and
     FAST re-boots.  There are several  solutions to the out
     of memory  problem:  use  less  buffering,  use smaller
     transients, or, of course, buy more memory.

DISK WRITE ERROR
     This message is  printed  when  FAST  attempts to write
     data to disk and gets  the unsuccessful completion flag
     back from the BIOS.  The only  recovery action taken is
     simply the  printing  of  the  message,  then execution
     continues normally.  This  usually indicates  a serious
     error (like a protected disk)  and the user should boot
     and take corrective measures as soon as possible.

INVALID OPTION
     This message is  printed whenever an  error is detected
     in the option string being scaned by FAST.  This may be
     the option string supplied  on the command  line or the
     default option string  in memory in  the unlikely event
     that it has  been incorrectly  modified.  Some examples
     of invalid options  are the  null option  ([]), options
     containing invalid characters  ([Q]), or  options which
     specify buffering of the  same type for  the same drive
     twice ([ABA]).

MEMORY HIT
     This message is printed whenever FAST attempts to write
     to a memory location  and cannot  read the  data it has
     just written.  The  recovery action  taken is  to print
     the message and  ignore  the  error.  It  is usually an
     indicator of  hardware  problems  in  your  system  and
     should  be  looked  into  immediately.  If  MEMORY  HIT
     errors are  persistent and  you have  a ROM  monitor in
     your system, you can  use FAST to  help find the memory
     at fault.  Create a  special  FAST.COM  with  a jump to
     your monitor patched into location 521H.  This location
     is called  when  a  memory  hit  is  detected.  The  HL
     register contains the address of the bad byte and a bit
     in the A register is set for each bad bit in memory.







FAST Users Manual    5/29/79                Page 8
FAST messages

              MEMORY ALLOCATON


When FAST is  loaded, it  automatically relocates  itself to
the top of  the TPA  (just like  DDT and  SID).  This action
overlays the CCP.  A side effect  of this is that transients
which normally return to  the CCP without  booting will boot
when executed under  FAST.  An example  of such  a transient
command is LOAD.


As mentioned earlier, the only way a transient can tell that
it is being executed under FAST is  that the size of the TPA
is decreased.  The amount of memory taken  out of the TPA by
FAST is  dependant  on  the  number  of  buffers  which  are
allocated.  The formulas used  to  determine  the  amount of
memory used are:

buffers = NTB * (3 + 131 * SPT) + NSB * (3 + 131 * SID)
SID = NDE / 4
mem used = 768 + [buffers]

Where:
    NTB  is the Number of Track Buffers allocated
    SPT  is the number of Sectors Per Track
    NSB  is the Number of Sector Buffers allocated
    SID  is the number of Sectors In the Directory
    NDE  is the maximum Number of Directory Entries
    [ ]  indicate rounding up the next highest
      multiple of 256

For a normal 8  inch  IBM  compatible  version  of CP/M, all
these computations can  be replaced  by a  simple estimating
rule:

     Allow 768 bytes for FAST code overhead, 3409 bytes
     for each track buffer (R or W), and 2099 bytes for
     each seek buffer (S).

As an example, FAST  executed without a  command line option
string will use  768 +  3409 +  2099 bytes.  If  this sum is
rounded up to the  next multiple  of 256,  the actual memory
usage figure becomes 6400 bytes.