December 9, 2011

On The BELLMAC-32, And Perhaps The World's Largest Plotter Pen Drawing

BELLMAC-32A Layout in the Ball Labs, Murray Hill Lobby, image:

Look closely, at least until I can track down a larger version of this snapshot.

Because it may be the world's largest plotter pen drawing.

It's a 20x20-foot layout of the BELLMAC-32, the world's first 32-bit microprocessor, developed by AT&T just before they divested themselves of Bell Labs and the RBOCs beginning in the late 1970s.

BELLMAC-32A microphotograph, via

According to a first-hand history of IEEE fellow Dr. Sung Mo (Steve) Kang, developing the BELLMAC-32 constantly uncovered the limitations of the design, testing, manufacture, and QA process for microprocessors:

Chip layout verification was another huge challenge. At that time, no CAD tools were available for the entire chip layout verification. As a result, we had to generate many CALCOMP plots and Scotch-taped them together to form a 20-foot-by-20 foot plot that was placed on the floor in a huge room. To make sure interconnects were formed properly, all terminals were labeled and wires were traced by using color pencils to make sure the lines ran continually. Although primitive, this method uncovered many errors and, in the end, produced error-free layouts and fabricated chips. We used a huge empty room in Building 3 of AT&T Bell Labs at Murray Hill or the main lobby area to complete the checking.
I love that creating the most advanced computer chip of the day still involved PhDs crawling across the floor with colored pencils.

Still from Microprocessor for the Information Age, a 1982 industrial film on the making of the BELLMAC-32, via AT&T's Archive

And of course, there's the giant drawing itself, spit out by a printer in tiles and taped together. Was Wade Guyton even born when this all went down? Yes, but still. So awesome.


Now to track down a working CALCOMP plotter and recreate it. Because it's probably too much to hope that AT&T or one of their computer engineer diaspora rolled all those sheets up and stuck them in their moisture-free basement. Right?

Microprocessor for the Information Age (1982) [ thanks reader robin edgerton]
First-Hand: The AT&T BELLMAC-32 Microprocessor Development []
previously: Shatner, plotter art, and the drawing machine as seen at the beginning of the digital age

Since 2001 here at, I've been blogging about the creative process—my own and those of people who interest me. That mostly involves filmmaking, art, writing, research, and the making thereof.

Many thanks to the Creative Capital | Warhol Foundation Arts Writers Program for supporting that time.

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