23680RE: [midatlanticretro] 50 years of Computer Games
- Dec 6, 2011David Gesswein wrote:
> Vector without display lists you need to rewrite everything at 30+ HzI'm thinking a vector display with a display list. The SWTPc SS-30 bus
> to prevent flicker.
provides a 4 byte interface per slot. I'm thinking a of programming
interface something like:
<low byte> vertex address
<next byte> vertex X
<next byte> vertex Y
<high byte> vertex options
vertex options would be something like:
<low 4 bits> intensity to this vertex (0 is off)
(do vector displays support intensity?)
<next bit> 0 - no action
1 - terminate (go back to vertex zero)
<next 2 bits> unused
<high bit> 0 - X,Y is absolute, X and Y are unsigned
(vertex zero must be absolute?)
1 - X,Y is relative to previous vertex, X
and Y are 2's comp signed
So, you poke a vertex address, then poke its three values.
I'm not sure how "coarse" a 256x256 vector display would be.
With relative vertexes (vertices?) moving the ships around the screen
will require a fewer operations. Rotations will still be painful.
I have no idea how realistic this will be to implement in hardware...
I know it would be easy with a modern pic, but I think I want to try
to go with a vintage design. Memory wise, it seems doable. It doesn't
even require 1K. I could implement it with a pair of 2114 static RAMS.
It might glitch during I/O. I could put 2K on the board and bank swap
to commit the writes. Then I need something on the board, spinning
through the RAM, driving three DtoA circuits? And a clock? I need to
do some reading.
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