BBS Toolkit/BBS Toolkit.iso/gt_power/gttutors.zip/GTTUTOR4.TXT

Text File | 1987-06-22 | 21KB | 345 lines

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Part four in a series of tutorials concerning communications  and
the  micro-computer  industry.   This  particular  tutorial   was
created during a call from Mr. Bruce  Aldrich  and deals with the
concepts of multi-tasking and the future of Local Area Networks.
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A:   James,  a few questions regarding the future  of  PC  multi-
tasking.

1)  Are  you  familiar with a new software product  for  the  386
called PC-MOS (I believe)?

2)   Are  you familiar with DRI's Concurrent DOS (as  well  as  a
just-out update by a different name which currently escapes me)?

Obviously,  I  am  interested in exploring  the  area  of  multi-
tasking.

D: If you will permit me, I would like to digress  and  establish
some  fundamentals  before answering directly.  I  wish  to  talk
about what has happened in the micro-computer world, and why,  in
order to develop a reasonable insight into where it is going.

About  the time of the introduction of micro-computers  into  the
marketplace  the manufacturers had recognized a long  term  trend
that needed to be continued: about every four years the  industry
was  providing  three times the  prior  performance/capacity  for
price increases of only about double the prior cost - unit  costs
were  decreasing..  The trend had taken computers into the  early
seventies in three broad forms:

1)  The  largest  form were (and still  are)  called  mainframes.
Entry  level  cost  was about a  million  dollars.   For  several
million  you  could get a mainframe that  could  support  several
thousand  simultaneous  users of that system.   It  cost  another
million or so per year to maintain that system (air conditioning,
raised  floor  and  other  capital  cost  amortizations,  systems
engineers, programmers, librarians, etc.).

2)  For  an  order of magnitude  less  money,  about  one-hundred
thousand dollars, you could buy a relatively small mini-computer.
For  several  hundred  thousand dollars you  could  buy  a  mini-
computer that could support several hundred simultaneous users on
that system.  It took about a hundred thousand dollars a year  to
support   the   initial   investment   (environment,    supplies,
programmers,  operators,  etc.).

3)  Finally, an order of magnitude less was required to  purchase
a  micro-computer.   Unlike the other two kinds of  systems,  the
micro-computers  could not support multiple users.  On the  other
hand,  unlike  the  other kinds of computers,  it  did  not  take
thousands of dollars per year to maintain such a computer.  There
were   no  environmental  requirements.   There  were  no   major
programmer  or operator costs.  In fact, what you could  buy  for
about  $10,000  was a single user computer.   Thus,  they  became
known as personal computers.

Well,  that  all  may have been obvious, but  looking  under  the
covers,  so  to  speak,  it  is  interesting  to  note  that  the
manufacturers  of  these  micro-computers  did  not  expect   the
business  community to be interested in them.  Their real  intent
in  bringing  these  machines to market  was  to  get  sufficient
manufacturing experience that they could quickly get in front  of
the  efficiency  ramp  up curve and,  through  volume  sales,  to
generate  economies of manufacturing scale such that  they  could
manufacture yet another generation of computers below the  micro-
computer level and to do so not for one order of magnitude  price
decrease,  but two!  They wanted to be able to produce  and  sell
micro-computers  (chips,  actually) that would be priced  not  at
$1,000  each, but at something closer to $100.  The layman  seems
not to  appreciate the fact that they were completely  successful
in their efforts.  You cannot buy a $30,000 automobile today that
does not have at least one $25 computer in it.

To  get  the volume of sales high,  the  manufactures  introduced
those computers as game players for home use.  That generated the
initial  bad  name  for  micros and  the  initial  resistance  by
business to use them.  Who would risk part of his business career
on a decision to use game players for serious work?

An  interesting thing happened soon after  these  micro-computers
began to sell in volume; they were found to be MORE reliable than
their larger cousins - of course, they had much less  complicated
circuitry,  many  fewer  components,  and  required  low   power.
Further, and this is the MOST IMPORTANT DEVELOPMENT OF ALL, there
emerged  an  INDUSTRY  STANDARD  called  the  S-100  bus.    This
permitted  many different manufacturers to enter the  marketplace
with  new peripherals, clones, and most important, with  software
that ran on almost all of these early 8-bit machines.

As  clever engineers recognized that these machines were able  to
perform several hundred thousand machine instructions per  second
and the vast majority of that capability was not being used, they
looked for ways to do so.  Let me explain that a little more.  In
these  early  machines  the typical  computer  program  (game  or
wordprocessor) was doing something like this:  I need a character
from  the keyboard, I'll see if one has been typed.  No,  nothing
yet.  Well, I need a character from the keyboard, I'll see if one
has  been  typed.   No, ..."  In other  words,  though  it  could
perform  several hundred thousand instructions per second it  was
almost always crawling along at the speed of the human operator's
typing skill - SLOW!

The  engineers  built  clever new  programs  that  would  control
several different programs at the same time in memory.  Of course
these  were only able to run one at a time, but whenever  one  of
those  programs needed to read a character from the keyboard  and
find  that none had yet been typed, or need to print a  character
to  the screen or a printer only to find that the  output  device
was  not yet ready to print it, the program would be  temporarily
stopped  and the system made to go to the next program in  memory
to  see  if it was capable of doing some work.  This  process  of
appearing to run more than one program at a time is called multi-
tasking.  In human terms it was extremely fast.  The result,  the
computers  were performing much more work than they had prior  to
multi-tasking.

But  there  were some real limits to this approach.   After  all,
there was only one central processing unit (CPU) and at most  you
could  have  only  64K of memory that had to  be  shared  by  the
programs.

Remember  I just mentioned that there was an  important  industry
standard that emerged from the mass sale of micros called the  S-
100  bus?   Well this was the enabling event that made  the  next
method of increasing the performance of these small machines.  S-
100  bus cards were introduced that contained on the single  card
both a separate CPU and 64K of memory that was dedicated to  that
CPU.   These  cards  became known as  'slave  systems'  and  were
plugged  into the same S-100 bus as the original CPU and  memory.
(A  'bus'  is merely a set of parallel wires with  connectors  on
them that allow every card plugged into them to have exactly  the
same data available to each of its pins as do all the other cards
connected to those lines.)  The original CPU became known as  the
'master system' or 'server' and became responsible for allocating
work  out to each of the other CPUs on the bus (that is why  they
were called 'slaves').  In this way a great deal more performance
was  made available from that micro than previously.  I must  add
that it also meant that a special and more complicated  Operating
System was required as well.

What  I  just described was the beginning of  what  the  industry
called  'tightly  coupled'  systems.  These  systems  had  common
access  to all the system memory and all the  peripheral  devices
attached  to  the  system.  Further, they  also  had  a  terminal
attached   to  each  of  the  slave  CPUs  and,   thus,   several
simultaneous users of the system was now a reality.  Recall, only
a  few years earlier it would have cost several hundred  thousand
dollars  worth  of  computer in order to support  more  than  one
simultaneous  user of a computer.  This was a  breakthrough  that
brought serious attention from the business community.

Looking more closely at those configurations, what was  happening
was  that  all  of the expensive devices  that  once  were  being
dedicated to only a single user were now being shared.   Printers
and  disks are the most obvious examples.  Along with sharing  of
devices came the obvious problems of controlling shared  devices.
It  would  not  do at all if two of the  users  wanted  to  print
reports at the same time and having, say, only one printer, being
allowed  to do that.  Thus was born buffers and  sequencers  that
made the user think he was printing but which in reality were re-
directing  output  destined to a printer and putting it  on  disk
someplace  to await a time when the printer was no  longer  being
used  by  another  user.  These were called  'spoolers'  and  the
concept is fundamental to the successful sharing of printers even
in  the  mainframes today.  Disk sharing brought with it  a  more
subtle  form  of problem; the possibility that  two  users  might
inadvertently corrupt the information required by each other.

For  example, assume that there is a client file on a disk  drive
that contains only one record in it and that that record contains
the current balance due by that client to the firm.  Suppose that
an accounts payable clerk is operating one terminal and wants  to
post a $1,000 payment received just as a sales entry clerk  tries
to  post  a new credit purchase of $500.   Finally,   assume  the
record  starts  with a balance due of $2,000.  If both  of  these
clerks happen to read the current balance due at almost the  same
time  they would put into their memory the record that says  that
they  are starting with a balance due of $2,000.  Let's say  that
the  sales  entry clerk posts the new purchase of  $500  to  that
record and saves the resulting $2,500 record back onto the  disk.
Then  the accounts receivable clerk posts the check  received  of
$1,000  to  her  copy of the current balance  (which  still  says
$2,000)  and then saves the resulting new balance due  of  $1,000
back  to  the disk (right on top of the old  one).   The  obvious
result is that the record of the new sales has been lost for when
either  of these clerks next reads the disk record it  will  show
$1,000  rather than $1,500 as it should.  This insidious  problem
is  solved  with the implementation of what is  called  file  and
record interlocks.  With these functioning properly no more  than
one person may ever have the ability to modify a disk record at a
time.  Unfortunately, even today, most software does not consider
that  this  might be a problem and does NOT use file  and  record
interlocks!

Along  came the 16 bit machines now generically called  the  PC's
(because IBM called their machines the Personal Computers  rather
than  game  players - good move!).  Besides  being  faster  CPUs,
these  machines broke through the 64K maximum memory barrier  and
thus  had much more satisfactory performance available  for  both
multi-tasking as well as multi-use of the computers.  Though they
were  much better equipped to handle these  performance  oriented
uses  of the computer, the software did not support it!   Indeed,
the user community was set back almost four years as a result  of
the  failure  of the hardware industry to work closely  with  the
software  industry  in order to meet the needs  of  their  users.
Many  believe it was a conscious effort designed to sell as  much
'iron' as they could before the prices of that equipment fell due
to competition.  Remember, in a single user environment there are
no shared devices.  Every user that wanted to print something had
to buy a printer.

For  several  years after the introduction of the 16  bit  micro-
computers the manufacturers of the 'old' 8-bit machines continued
to  advance  their  capabilities.  As I  mentioned  earlier,  the
ability  to  support  multiple users at the same  time  had  been
introduced  BEFORE  the  16-bit  machines  were  even  announced.
Development  continued  in  a new  direction,  however.   It  was
already seen that they had reached certain limits in terms of how
many  cards  could  be plugged into the same  S-100  bus  and  be
expected  not  to  dramatically impact the  performance  of  that
single bus due to conflicts and simultaneous demands of it.   The
new  approach  was  called 'loosely coupled'  systems.   In  this
method  of  sharing  of  resources  (notably  printers  and  disk
devices) complete computers were tied together via coax cable and
elegant software.  Messages were routed from one computer to  the
next over those cables.  Sometimes they were arranged in loops or
rings,  without  'ends'.   Sometimes they were  arranged  with  a
central  computer  in the center and the remotes at the  ends  of
cables as 'stars or 'spokes'.  Whatever the configuration of  the
cabling,  the  result  was that a user of any  of  the  computers
connected  to the cable could send print jobs to shared  printers
(spooling as necessary) and read or write files from disk  drives
that  were  located on other computers (typically the  master  or
server).  And as you might expect, before long there evolved  the
ability  to connect one such NETWORK of computers to another  one
that  was  located either near by or sometimes  several  thousand
miles  away  via telephone connections  (these  connections  were
called 'gateways').

And  what were the bigger 16-bit computer manufactures doing  all
this  while?  They were selling a lot of  micro-computers  (based
largely  on  their  names (IBM, DEC,  WANG)).   Finally,  several
companies  that  had  pioneered  the  development  of  multi-user
capabilities   in  the  8-bit  machines  and  network   component
manufactures upgraded to the 16-bit machines.  3COM, Novell,  and
several  others announced NETWORK capability for the PC's (as  if
it  was the best thing since night baseball and  something  new).
It  was not met with great enthusiasm by the business  community.
Primarily since IBM and the other computer manufacturers had been
so successful in convincing these buyers that a machine on  every
desk  was  the wave of the future and because they did  not  have
their  own networking capability at the time, it  was  pronounced
'premature'   to   leap  into   a   potentially   'non-standard',
potentially  'dead-ended' approach such as were being offered  by
these  network  manufacturers.   IBM  soon  announced  their  own
network  architecture which was the worst of the bunch and a  few
years  later they admitted that there was a better way and  'pre-
announced' exactly how businesses should wire their buildings  to
prepare  for their new network architecture.  It turns  out  that
that architecture changed after IBM's more loyal clients had done
as IBM recommended, but that is another story all together.

The message I am trying to get to is that it is still  pre-mature
to  bet  on  a  specific  network  architecture  (loosely  couple
systems).   Further,  tightly coupled systems have  been  TOTALLY
ignored by IBM as they are simply too efficient and do not result
in  other  than incremental hardware sales.   Finally,  with  the
introduction of Intel's 80286 CPU the 16-bit micro-computers were
able to very efficiently operate in multi-tasking mode  (remember
how it all started with the 8-bit machines).

IBM did not make software available to run multi-tasking on their
machines that was compatible with the existing software (PC-DOS).
Instead,  they 'introduced' UNIX as the software  that  permitted
multi-tasking  of  their machines.  Indeed,  there  were  several
'flavors' of this massive and highly inefficient Operating System
that soon became available (ZENIX is a UNIX derivative or clone).
In  other words, the industry as led by IBM began to  forget  the
value  of  standards  and  started  pushing  software  that   was
incompatible   and   which  not-coincidentally   required   major
increases  to  the amount of memory and disk space  available  to
then  in  order  to operate.  That strategy  has  not  been  well
received  and  PC-DOS and MS-DOS are still by  far  the  dominant
Operating Systems on the PC/XT/AT micro-computers.  Multi-tasking
needs are usually supported via off-brand software houses such as
DoubleDos,  DESQview, and Multi-Link.  IBM introduced,  late  and
poorly  done,  and inefficient as usual,  a  multi-tasker  called
TopView, described by IBM as an emerging standard, but in reality
a  failure  in  the marketplace.  Other  multi-taskers  are  also
available today such as Windows.

And  then  came the super micros which use the Intel  80386  CPU.
This machine can often run as much as 17 times faster than  IBM's
original PC and can support a dozen megabytes of memory and more.
It is clearly the mainframe in miniature dreamed about only a few
years  ago.  And still there is no standard available for  multi-
tasking, for tightly coupled or loosely coupled multi-user needs,
and  one  full generation of CPU (the 286) has  had  capabilities
that are important (virtual memory and protected software shells)
that  may  never be supported with software.  That  is,  the  286
family of machines exist almost exclusively as faster PC's and so
too do the 386's installed.

Why?  Well perhaps the fact that IBM announced the PS/2 (Personal
System/2)  family  of micro-computers has something  to  do  with
that.   Perhaps in their zeal to force proprietary 3 1/2"  floppy
disks  onto the public in order to force the  clone  manufactures
out of business they failed to consider the needs of the existing
computer owners.  Perhaps IBM has all the answers and is about to
bring them to the market after all.

Which  reminds me of the story of the most unfortunate woman  who
had  been married three times and still claimed to be  a  virgin.
Asked how that was possible she answered that the first time  she
married  she  was young and so was her husband.  On  the  wedding
night  they  had partied a bit too much and after  a  tragic  car
accident  she  was  left widowed and the marriage  had  not  been
consummated.  The second time she married it was her decision  to
play  it  safe.   She married an older man  who  was  financially
secure  and stable - didn't even drink.  Unfortunately he  was  a
bit too old and on their wedding night he died of a heart  attack
just  after  she had removed her clothes - widowed for  a  second
time  without consummating the relationship.  The third time  she
married  an IBM salesman.  He was in his mid  twenties,  healthy,
good  looking, and apparently eager.  They had been  married  for
six months before she filed for divorce as the marriage  remained
unconsummated.   Asked why she said that every night it would  be
the  same old thing; he would get into bed and tell her how  good
it was going to be.

Yes,  Bruce, I have heard of the products you mentioned.   In  my
opinion  you should be more interested in the  established  Local
Area Networks than in these products to satisfy the longer  range
needs  of  your  client.  3COM Plus or  Novell  are  the  leading
contenders  and  they  both  have  highly  reliable  and   highly
efficient  LAN capabilities.  Multi-tasking is supported only  on
the  server  and is reserved for the support of the  slaves,  not
end-user  work.  Tightly coupled systems are more cost  effective
than  LAN but suffer from a lack of standards and finite  (small)
number of simultaneous users.  Wish I could be more helpful.