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Compiled and written by Steven Weyhrich
(C) Copyright 1991, Zonker Software

[v1.1 :: 12 Dec 91]


     Let's put some more trash into Mr. Fusion to fuel the next leg of our
trip.  How about one of those KIM-1 computers over there in the corner of
the Computer Faire auditorium?  We might have to break it up a bit to make
it fit... Okay, now we'll just make a small jump, to December of 1977.  
By this time the AppleII had been generally available for about six
months.  Most customers used their television as an inexpensive color
monitor, and used a cassette recorder to store and retrieve their programs
and data.  Apple's major competitors were the TRS-80 and the Commodore
PET.  The products made by these two companies, together with Apple, could
be considered as the second generation of microcomputers; they all came
fully assembled and ready to use out of the box, with a keyboard and
cassette interface.  The TRS-80 and the PET even came with a monitors and
cassette recorders.  The strength of the Apple was expandability and
graphics, while the strength of the others was cost (both the TRS-80 and
the PET sold for around $600, half the price of the AppleII).

     By late 1977, Apple had introduced some enhancements to the II,
including their first version of a floating point BASIC (called
"Applesoft") on cassette, and a printer interface card to plug into one of
the slots on the motherboard.  But the AppleII still needed something to
make it more attractive to buyers, to stand out above the TRS-80 and the
PET.  One area that needed improvement was its program and data storage
and retrieval system on cassette; it was a continued source of frustration
for many users.  The cassette system used on the TRS-80 was more
sophisticated than that of the AppleII, allowing named files and easier
storage of files and data on the same tape.  On the AppleII it took VERY
careful adjustment of the volume and tone controls on the cassette
recorder to get programs or data to successfully load.  The Apple cassette
system also needed careful attention to the location on the tape where a
program was stored, and was no more accurate than the number on the
recorder's mechanical tape counter (if it had one).

     Apple president Mike Markkula was one AppleII user that was
dissatisfied with cassette tape storage.  He had a favorite checkbook
program, but it took two minutes to read in the program from the tape, and
another two minutes to read in the check files.<1> Consequently, at the
executive board meeting held in December 1977 he made a list of company
goals.  At the top of the list was "floppy disk".  Although Wozniak didn't
know much about how floppy disks worked, he had once looked through a
manual from Shugart (a Silicon Valley disk drive manufacturer):

"As an experiment Woz had [earlier] conceived a circuit that would do much
of what the Shugart manual said was needed to control a disk drive.  Woz
didn't know how computers actually controlled drives, but his method had
seemed to him particularly simple and clever.  When Markkula challenged
him to put a disk drive on the Apple, he recalled that circuit and began
considering its feasibility.  He looked at the way other computer
companies--including IBM--controlled drives.  He also began to examine
disk drives--particularly North Star's.  After reading the North Star
manual, Woz knew that his circuit would do what theirs did and more.  He
knew he really had a clever design."<2>

     Other issues that Wozniak had to deal with involved a way to properly
time the reading and writing of information to the disk.  IBM used a
complex hardware-based circuit to achieve this synchronization.  Wozniak,
after studying how IBM's drive worked, realized that if the data was
written to the disk in a different fashion, all that circuitry was
unneeded.  Many floppy disks sold at that time were "hard sectored",
meaning that they had a hole punched in the disk near the center ring.  
This hole was used by the disk drive hardware to identify what section of
the disk was passing under the read/write head at any particular time.  
Wozniak's technique would allow the drive to do self-synchronization
("soft sectoring"), not have to deal with that little timing hole, and
save on hardware.

     Wozniak asked Randy Wigginton for help in writing some software to
control the disk drive.  During their week of Christmas vacation in 1977
they worked day and night creating a rudimentary disk operating system,
working hard to get the drive ready to demonstrate at the Consumer
Electronics Show in the first week of 1978.  Their system was to allow
entry of single letter commands to read files from fixed locations on the
disk.  However, even this simple system was not working when Wozniak and
Wigginton left for the show.

     When they got to Las Vegas they helped to set up the booth, and then
returned to working on the disk drive.  They stayed up all night, and by
six in the morning they had a functioning demonstration disk.  Randy
suggested making a copy of the disk, so they would have a backup if
something went wrong.  They copied the disk, track by track.  When they
were done, they found that they had copied the blank disk on top of their
working demo!  By 7:30 am they had recovered the lost information and went
on to display the new disk drive at the show.<3>,<4>

     Following the Consumer Electronics Show, Wozniak set out to complete
the design of the Disk II.  For two weeks, he worked late each night to
make a satisfactory design.  When he was finished, he found that if he
moved a connector he could cut down on feedthroughs, making the board more
reliable.  To make that move, however, he had to start over in his design.  
This time it only took twenty hours.  He then saw another feedthrough that
could be eliminated, and again started over on his design.  "The final
design was generally recognized by computer engineers as brilliant and was
by engineering aesthetics beautiful.  Woz later said, 'It's something you
can ONLY do if you're the engineer and the PC board layout person
yourself.  That was an artistic layout.  The board has virtually no


     The Disk II was finally available in July 1978 with the first full
version of DOS, 3.1.  It had an introductory price of $495 (including the
controller card) if you ordered them before Apple had them in stock;
otherwise, the price would be $595.  Even at that price, however, it was
the least expensive floppy disk drive ever sold by a computer company.  
Early production at Apple was handled by only two people, and they
produced about thirty drives a day.<6>,<7>

     Apple bought the drives to sell with Woz's disk controller from
Shugart, right there in Silicon Valley.  To cut costs, however, they
decided to go to Alps Electric Company of Japan and ask them to design a
less expensive clone.  According to Frank Rose, in his book "West Of

"The resulting product, the Disk II, was almost obscenely profitable:  
For about $140 in parts ($80 after the shift to Alps) [not counting labor
costs], Apple could package a disk drive and a disk controller in a single
box that sold at retail for upwards of $495.  Better yet was the impact
the Disk II had on computer sales, for it suddenly transformed the AppleII
from a gadget only hard-core hobbyists would want to something all sorts
of people could use.  Few outsiders realized it, but in strategic terms,
Woz's invention of the disk controller was as important to the company as
his invention of the computer itself."<8>





     <1> Gregg Williams and Rob Moore, "The Apple Story, Part 2: More
History And The AppleIII", BYTE, Jan 1985, pp. 167-168.

     <2> Paul Freiberger and Michael Swaine, "Fire In The Valley, Part Two
(Book Excerpt)", A+ MAGAZINE, Jan 1985, p. 45.

     <3> Williams and Moore, "Part II", p. 168.

     <4> Freiberger and Swaine, (Part Two), p. 45.

     <5> Freiberger and Swaine, (Part Two), p. 46.

     <6> -----, "A.P.P.L.E. Co-op Celebrates A Decade of Service",
CALL-A.P.P.L.E., Feb 1988, pp. 12-27.

     <7> -----, "Apple and Apple II History", THE APPLE II GUIDE, Fall
1990, pp. 9-16.

1989, pp. 62.


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