'bug' in G80 vector generator

I just fixed a corner case in my simulation which revealed an interesting
bug in the G80 hardware. I wasn't testing for 'last symbol' until after
the first symbol was finished. Guess what, they don't either! It appears
that the first symbol is ALWAYS drawn from the symbol list (sort of makes
sense thinking about the way the state machine works in the hardware) and
it turns out that Space Fury isn't real good about keeping the valid bit
set on the first symbol, some screens have it set and some don't.

..just thought you'd all like to know (and i'll add it to the FAQ).

I'm about halfway through rewriting the blitting code in the simulator to
be much smarter about redraws by keeping track of 8 * 8 blocks of pixels
on the offscreen bitmap and only blitting the blocks that have changed.
I'm also adding an antialiased vector drawing routine which should get
rid of that nasty jitter you see as things scroll up and down (like the
instructions in Space Fury).
Received on Wed Jun 4 17:24:56 1997