CDC 6600 display character generation

[Paul Koning]

> On Jun 6, 2018, at 5:17 PM, Jim Manley via cctalk <cctalk at classiccmp.org> wrote:
> 
> ...
> I'm one of the early senior docents at the Computer History Museum in
> SillyCon Valley and yammered on endlessly about the 6600 and its neighbor,
> the 7600, but I never thought about character generation on the displays
> beyond it being vector-based drawing.  I'm pretty sure it was done via
> look-up tables that directed the beams along vectors on the displays for
> the operating PDP-1 we play Spacewar! 

The crazy thing about the 6000 series display controller is that it doesn't use tables at all.  The selection of what stroke step to produce for a given character and point in time is defined by a very large collection of gates.  The 170 controller does use table lookup (a ROM with the equivalent information).  I wonder why a ROM wasn't used in the 6000.  Perhaps they couldn't find a cost-effective technology that's fast enough?  Core rope would work just fine for this, but not at 100 ns cycle time.

	paul