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The Commodore 64
from
On The Edge:
The Spectacular Rise and
Fall of Commodore
by Brian Bagnall
Part I
1981 - 1982
With less than two months to build
a complete computer system
(temporarily named the VIC-40), the
engineers rarely left the MOS
Technology building. "In the middle of
the building lab, we took over one
corner of the room and worked 20 hours
a day, 7 days a week to get the
prototypes running," says Robert
Russell
As managers, Charles Winterble and
Al Charpentier did not perform
hands-on work on the VIC-40. "It was
Bob Yannes, me, and Dave Ziembicki the
technician who really went off and did
the Commodore 64," says Russell.
"Luckily we had a guy like Charlie
Winterble who let us go off and do
that when we were supposed to be
making the P and B stuff work."
Designing a full computer system
was a new challenge for Bob Yannes. "I
was still in the chip group so I
wasn't really supposed to be working
on systems," says Yannes. "The only
reason I ended up doing the C64 was
because I was the only one who knew
enough about the chips and how to put
them together in a timely fashion."
With such a tight schedule, Yannes
and Russell began laying out the
architecture of the computer. "Bob
(Yannes) and I sat down and came up
with the hardware architecture,"
recalls Russell.
Yannes was an assiduous engineer
by nature. For two short days, Yannes
worked in his office and the drafting
area to design the architecture for
the VIC-40. "It was a pretty easy
architecture," says Yannes. "I just
designed the most minimal system I
could with the fewest number of
components. There's not a whole lot of
stuff in there. There's the VIC chip,
the SID chip, and there's 64K of
DRAM."
Almost none of the design came
from the VIC-20. "There were very few
chips that were used in the C64 that
had ever been used before," says
Yannes. Only the serial port, cassette
port, and user port remained the same.
It also used the same joystick
connecter, except there were two.
Rather than use the same bulky
cartridge system of the VIC-20, Yannes
decided to borrow technology from the
Max Machine. "Since the Max Machine
was already in progress, I decided to
make one of the C64 memory
configurations match the Max so that
it would be able to use Max game
cartridges," explains Yannes. "When
you plug the game cartridge in, it
would automatically collapse the
memory map of the Commodore 64 to look
like the Max Machine."
The VIC-40 was essentially a
computer with a game console built
into memory. The engineers wondered
how they could create such a complex
memory layout before CES. They found
their salvation in the Programmable
Logic Array chip (PLA). According to
Russell, "I remember finding that chip
and saying, 'Oh, that will do exactly
what we want!'"
The PLA chip acted like glue to
hold the different parts of the system
together. Yannes could simply insert
the PLA chip and program it later. "I
didn't have time to design all the
logic before they laid the PC board
out, so I just took a PLA and named
the signals I needed and told them to
lay that out," recalls Yannes. "While
they were laying it out I could figure
out the coding for the PLA. That got
us to the show."
When engineers need to build a
circuit quickly, they use thin wires
and a special wire wrap tool to
connect the chips together. However,
Yannes believed it would be
inadequate. "You really couldn't do a
wire wrap with dynamic RAM because the
timing was too tight," says Yannes.
Instead, the engineers would fabricate
a printed circuit board.
To allow time to develop software,
Yannes left nothing to the last
minute. "We had to have a working
circuit board practically a month
before that to get the software
working because we wanted to show it
running with Basic," says Yannes.
"It was going to be perfect," says
Russell. "We made it simple and clean.
We cut boards and everything in one
month."
[Continued in Part II]