This is going to sound insane, but you can get an amazing and bizarre
look into what the VCS is doing by physically disassembling it and
pressing your hand against the underside of the processor board while a
game is running. What the processor is doing shows up on the TV as
various interference patterns. The best results I've had so far have
come from pressing one thumb against a couple of the pins leading to
the cartridge slot and the other against some of the resistors about
halfway down the side. (This is on a six-switch NTSC Sears dated July
28, 1980; your results may vary.)
What's going on, I think, is that your body acts as a large resistor,
letting you connect things (like the address bus and the video)
together in such a way that analog things like the color phase are
tweaked enough to be visible but digital signals are basically
unaffected. I'm going to have to go to Radio Shack tomorrow and
get some big resistors so I can examine this more systematically.
Tangentially, if I ever had to pick a program to enter in a Core Wars
competition, the Parker Bros Frogger cartridge would be at the top of
my list. That game can take some amazing abuse (bus lines shorted
together, etc.) and still keep drawing a valid playfield in spite of
it all.
eric
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