Cyber 172
Never did touch a CDC 6600, but the first big machine I got to play with was a 6400. Those ASR33 Teletypes were such a Great Thing! Oh Boy! Interactive Computing with a rhythm sectin thrown in! Way too cool.
Later the University of Calgary acquired a Cyber 172 which (IIRC) was more or less an integrated-circuit update of the 6000 series hardware.
Regrettably I have no pictures of the 6400, but you can find a (rather poor) picture of the Cyber 172 console at:
http://www.cuug.ab.ca/~bramwell/cyber-172-console.jpg
I've seen the same display on a 6400 screen. The console display was driven by a dedicate PPU (Peripheral Processor Unit), basically a mini-computer that front-ended the CPU. At the time the console was the most advanced graphics device available on the system. I believe our configuration had 12 PPU's that mostly managed I/O peripherals.
One amusing oddity of the CDC machines was that one did not "boot" them: one performed a "deadstart":
http://www.cuug.ab.ca/~bramwell/cyber-172-deadstart.jpg
which loaded a program into PPU-0 (again, IIRC) from a panel of toggle switches.
They were fascinating machines, but I have to say I was glad to see the back end of the last one they wheeled out. The next box ran Multics....