Control Data 6600

"Last week Control Data ... announced the 6600 system. I understand that in the laboratory developing the system there are only 34 people including the janitor. Of these, 14 are engineers and 4 are programmers ... Constrasting this modest effort with our vast development activities, I fail to understand why we have lost our industry leadership position by letting someone else offer the world's most powerful computer."
-- Thomas Watson, CEO of IBM

"It seems like Mr. Watson has answered his own question."

-- Seymour Cray, Control Data Corporation

CDC 6600 Console

The console of the CDC 6600 had two vector graphics scopes. I played spacewar on one of these consoles, a very nice simulation of dynamics and gravity, but somewhat more expensive than an X-Box or Play Station! Behind the console is a row of high speed pneumatic tape drives. Tape drives like these were the iconic image of a computer at that time.

CDC 844 Disk Drives

A row of model 844 disk drives, each holding more than 200 mb. My friend and fellow hacker, Jeff Drummond, is standing in the rear. The CPU was never interrupted by I/O, instead peripheral units controlled the drives and communicated with the CPU via polling and circular message buffers.

Inside 6600 CPU

Seen from above the 10 MHz CPU was cross shaped, with four wings, each holding 4 door-sized panels of electronics. Above, you can see two panels, with hand-sized circuit cards plugged in. These were made from discrete silicon transistors. A floating-point multiplier was one entire panel, and the 6600 had two multiplier units.

The 6600 also had peripheral processing units (PPUs), a 12 bit minicomputer that executed multiple programs with a round-robin schedule, simulating 10 or 20 virtual machines. This and the hardware context-switch instruction in the CPU were interesting features supporting CDC's remarkably efficient timesharing operating system.

Below, you can see the back of a panel, a dense mat of wirewrap connects the pins on the circuit cards. On the right is power and refrigeration. The wirewrap was all the same color, there was just no point in trying to color code it!

Wire Wrap in 6600 CPU

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Copyright 2003 Don P. Mitchell. All rights reserved.