Hi guys,
Thanks to Curt's great archiving work, we have the designer's notes on The Graduate peripheral for the 2600:
http://www.atarimuseum.com/videogames/consoles/2600/a3000.html
They invented a 3-cycle "Bus Stuff" mode, to achieve an even faster TIA register update rate than the Harmony's 5-cycle/DPC+ "Fast Fetch" mode.
This works by loading Y with $FF at the beginning of the kernel, and then having the 6507 execute 3-cycle STY $REG instructions. At the critical moment when the