Loadstar 247/247.d81/t.tales of Kim 1

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             ON THE EDGE:
    THE SPECTACULAR RISE AND FALL
             OF COMMODORE
            Tales of KIM-1
           by Brian Bagnell


[Note: Brian extended his history of
Commodore computers to include some
exciting stories about the KIM I. We
simply had to bring this "half-
chapter" to you.]


          C H A P T E R 1.5

       TIM and KIM 1975 - 1976

    In introducing the 6502
microprocessor to the world, Chuck
Peddle knew he had something
revolutionary. As part of MOS
Technology's marketing plan to
encourage people to experiment with
the 6502, Peddle and his team at MOS
Technology would develop two small
computer systems, known as development
systems. "They worked on them while we
were finishing up the processor and
getting ready to do the marketing,"
explains Peddle. Engineers and
hobbyists, the idea went, would use
them to evaluate the 6502 instruction
set and develop their own systems.


 THE KIT

    The first development system
offered by MOS was in kit form, which
reduced the selling price to only $30.
Since the unit was designed primarily
to instruct the user on the workings
of computer systems in general and the
6502 in particular, MOS Technology
contracted Microcomputer Associates of
Santa Clara, California to write the
unit's internal program. The two
founders, Ray Holt and Manny Lemas,
taught engineers how to use
microprocessors.

    Peddle relates, "You have to
understand how little the world knew
of microprocessors in 1974, '75 and
'76. There were guys making big money
selling classes on microprocessors
during that time." Manny Lemas had
worked for Peddle during his GE days,
while Ray Holt had an impressive
background working on the F-14 Tomcat
project for the Navy. (Holt claims he
invented the world's first
microprocessor for the Navy in
November 1969, approximately a year
before Intel. Security restrictions by
the Navy prevented him from disclosing
this until 1999 - by which time most
people accepted that Intel was the
first.)

    The technicians developed the
system in a special research area on
the second floor of MOS Technology.
The lab was a room within a room, with
a large sign on the door in capital
letters warning NO ADMITANCE. Inside,
the team stared intently at
oscilloscopes or sat over hot irons
soldering components onto circuit
boards. Small pieces of circuitry were
scattered chaotically across the room.
Since the 6502 microprocessor and
supporting chipset contained almost
everything necessary for a computer,
the design was minimal. When
assembled, it could be connected to a
teletype machine or a computer
terminal.

    The biggest job was programming
the built-in ROM code for the
computer. This consisted of a debugger
and monitor program, appropriately
called the Demon.

    According to Peddle, Demon was
programmed by Manny Lemas and Mike
Quarter, who previously developed
Peddle's time-sharing system. The
programmers used this time-sharing
system to develop the code, which they
burned into a 6530-004 RRIOT chip.

    This little powerhouse included
RAM, ROM , I/O and timer capabilities.
The system was named simply. Peddle
and his team liked acronyms, thus the
Terminal Interface Monitor, or TIM was
christened. TIM would begin a
predilection at MOS Technology and
Commodore for assigning friendly
three-letter names to their products.

    Those ordering the $30 development
kit received the grey-ceramic 6530-004
chip and a manual consisting of 14
sheets of 11x17 paper, folded and
stapled in the middle. Included in the
manual were a suggested schematic, the
TIM monitor commands, a few sample
programs and a listing of the monitor
code. It was up to the user to provide
the resistors, transistors,
capacitors, wire, and even the 6502
microprocessor.

    Though receiving a computer in the
form of a kit does not seem
particularly user friendly now,
hobbyists at the time clamored to
build their own computer. Nonetheless,
a good portion of the kits failed to
operate upon completion. Rather than
using a prepared circuit board, many
buyers simply wire-wrapped the chips
together on a piece of generic perf
board or prototyping board, often
termed a kludge board. After placing
the required components on the board,
builders hand wired the chips one pin
at a time, resulting in a snarl of
fine multicolored wires.

    Once the chips were in place, the
user then had to construct or purchase
a separate power supply for the TIM.
Finally, the TIM was (as the name
suggests) able to interface with a
standard ASCII terminal or teletype
machine.

    As hoped, the do-it-yourself
nature of the kits spawned familiarity
with the products, and once hobbyists
had invested time learning about the
chip, they often remained loyal to the
6502. Many hobbyists ended up using
their TIM computer as a small
development system, since it was ideal
for creating small programs.

    For their part, MOS Technology
continued to sell TIM computer kits to
diehard hackers, even after the
Commodore acquisition. Ultimately, TIM
was just a stepping-stone to
developing and marketing a fully
assembled computer.


KIM-1

    MOS Technology developed a second
system concurrently with the TIM. This
computer was slightly more user
friendly - at least by 1975 standards.
Rather than a chip and some
instructions, this system arrived
fully assembled, except for the power
supply. It was a true development
system.

    The inspiration for the new
computer came from Don McLaughlin, MOS
Technology founder and engineering
manager of the project. Peddle
recalls, "McLaughlin said, 'Listen, I
think this is a product that will help
sell the 6502'. They thought it was a
good idea because they were calculator
guys." Peddle and a programming
manager named Bob Winterhalt agreed
with the idea and the three men began
the design.

    According to MOS Technology
employee Al Charpentier, his friend
and fellow engineer performed the
actual hands-on design work of the
system. "That was done by a guy by the
name of John May," recalls
Charpentier. "He was sort of the
primary mover on that project.

    At this early stage in micro-
computer development, user-friendly
personal computers were barely on the
horizon. Niceties like a video
monitor, keyboard, software, power
supply, or an enclosure were not part
of most designs. The recently released
Altair relied on switches for input
and blinking lights for output. Any
other interfaces had to be added by
the user. By today's standards, it was
comically impossible for most people
to contemplate using these machines.

    This new sibling of TIM would
share similarities, but differ in a
few areas. As with the TIM, this unit
would contain a 6502 processor running
at one megahertz. However, McLaughlin
advanced TIM's basic design slightly,
branching out in a unique direction.

    Instead of reading data from a row
of flashing lights, the new computer
would contain a six-digit display.
Each digit in the display had seven
segments, which could display numbers
and letters. The primitive display was
a step up from tiny lights
representing binary digits used on
most other systems.

    McLaughlin also improved on the
basic input method for personal
computers at the time. Rather than a
row of switches for binary input,
McLaughlin specified a keypad. John
May eventually selected a black keypad
with 23-buttons. This was a remarkable
improvement over other microcomputers
of the time, allowing users to enter
code more easily.

    Both the keypad and the LED
display reside directly on the surface
of the printed circuit board (PCB),
along with over a hundred precariously
exposed components. The lack of a case
or a power supply for the new computer
clearly indicated MOS Technology was
not targeting the machine for the mass
market. A careless user could easily
damage the machine.

    Little TIM provided a paltry 256
bytes of memory, hardly enough to
store three lines of characters on an
80-character computer display. TIM's
bigger brother would contain a full
kilobyte of memory, comprised of eight
MOS Technology 6102 memory chips. At
the time, 1024 bytes was a generous
amount. There was even room for
expansion. Two 44-pin edge connectors
made data and control signals
available to the builder for
additional functionality.

    Although the two development teams
were separate, they shared as much
code as possible. To support a
teletype machine, John May used the
code from the TIM system.

    The 2-kilobyte program, also named
TIM, contained the code to operate a
cassette tape unit for storage, drive
the alphanumeric display, and accept
input from the 23 keys of the keypad.
It also contained a monitor program,
which allowed users to view memory
contents and change code. A tiny
bootstrap program would automatically
start the monitor on reset. This was
the pinnacle of user friendliness in
1975.

    The name for this new computer
followed the tradition set by TIM. The
TIM allowed input from a terminal,
hence Terminal Input Monitor. The new
system allowed input from a tiny black
keyboard, so McLaughlin dubbed it the
Keyboard Input Monitor, or KIM. They
also added a number after the computer
name, a practice later continued by
Commodore. It contained one kilobyte
of memory, hence KIM-1.

    (Former MOS Technology engineer
Robert Yannes owns the first KIM-1. "I
have a very rare thing that I
scavenged out of scrap heap at MOS
Technology: the original prototype
KIM-1, and it still works. It's a
little bit different than what went
into production," he says.)

    In the middle of 1975, MOS
Technology began selling the KIM-1.
Buyers who sent away for their KIM-1
were pleasantly surprised to have a
rectangular cardboard box arrive from
"MOS Microcomputers", a short-lived
division of MOS Technology. The KIM-1
circuit board arrived sealed in a
black static-proof bag, surrounded by
thick foam padding with manuals and
documentation on top.

    The documentation included with
the KIM-1 went beyond other computers
of the day. There were three manuals -
a 200-page 6502 programming manual
(written by Peddle under duress), a
100-page KIM-1 user manual, and a
150-page hardware manual. The writing
was friendly, concise, and detailed.
Most importantly, it did not assume
the user knew everything about
computers already. The KIM-1 user
manual promised, "You should be able
to achieve initial operation of your
KIM-1 module within a few minutes."

    Of course, this assumed you had
access to a 5 volt, 1.5 ampere power
supply. A 12 volt supply was required
if the cassette tape was to be used.
For those in doubt, the manual
contained complete instructions and a
parts list for building a power
supply. Once the power supply dilemma
was solved, the user hit the RS
(reset) key to start using the system.
This started the TIM monitor program
running from ROM, which displayed
numbers and accepted input from the
keypad. Unlike today's systems, the
KIM-1 contained no on-off switch.

    Users then began the exacting
process of entering code into the
machine in order to make KIM do
something. After entering all the
data, it was simple to run the program
- just set the computer to the address
where the program began and hit the GO
button. If the program misbehaved, the
KIM-1 also had a switch on the keypad
labeled SST (single step). This would
cause the computer to execute the
program one instruction at a time.
Users appreciated this important
feature, which greatly assisted in
debugging.

    The built in cassette-tape
interface of the KIM-1 proved
indispensable for early hobbyists
because it allowed them to save and
load their work. In contrast, users of
the MITS Altair had no way to save
programs with their basic system. They
would sit in front of their machine,
laboriously flipping switches to enter
their program into memory. If someone
happened to trip on the power cord,
the programmer had to start all over
again.

    The tape-interface alone made many
KIM-1 owners fall in love with the
computer, and many praised it for its
reliability. Tape storage was the
perfect medium for a 1-kilobyte
computer. Programs loaded and saved
rapidly, and dozens of programs fit
onto a single cassette. Of course, a
cassette recorder was not included
with the KIM-1, so it was up to the
user to find one. It was also up to
the user to connect it to the KIM-1 by
interfacing the microphone input and
speaker output jacks to the
gold-plated IO pins of the KIM-1.

    Another advanced feature of the
KIM-1 was its ability to connect
directly to a Teletype machine or
computer terminal through a built-in
serial interface. Teletype machines
were large electromechanical devices
with the ability to enter data through
a keyboard, print hard copy, and load
and save data via punched paper tape.
A noteworthy feature of the KIM-1 was
its ability to automatically adjust to
the speed of the teletype connected to
it.

    People were amazed to see the tiny
KIM-1 operating a massive piece of
hardware normally connected to
minicomputers or mainframes. This
helped to convince skeptics that
microcomputers were true computers. As
it turned out, however, many people
preferred using the LED display and
keypad to the noisy, messy, and costly
teletype machines.


        [Continued in Part II]