Re: Sega Multigame and Vector Generator Card...

From: Paul Kahler <phkahler_at_Oakland.edu>
Date: Wed Dec 17 1997 - 09:46:15 EST

> The register file might be the toughest part. Each bit will take a
> Macrocell, so just a 4x24 consumes 75% of a 128 m-cell device. :-( A 24
> bit adder isn't exactly skinny either. I suppose there's tricks that can
> be played here though... You could keep the vectorlist in a large (32Kx8
> or 128Kx8 SRAM) and use a few bytes high in RAM to store the position
> counters, then just load the one you need at any given time. If you made
> an assumption that any delta value must be less than 1, you could
> accumulate delta's with a 12 bit adder and carry 1 with a separate 12bit
> add for the whole portion. Clock speed is on our side, so doing a bunch of
> operations isn't too much of a problem...

If the ram isn't fast enough, you can leave the last value read (a delta)
sitting on the data lines for the duration of the draw :-) I suppose we
can simulate the process by writing an equivalent line drawer for an
emulator - then we could test the required number of bits. I think 10.10
fixed point or *maybe* 10.8 would be enough. But I still want curves ;-)

--
 ___   __   _   _  _
|   \ /  \ | | | || |       phkahler@oakland.edu     Engineer/Programmer
|  _/| || || |_| || |__     " What makes someone care so much?
|_|  |_||_| \___/ |____)      for things another man can just ignore. " -S.H.
Received on Wed Dec 17 06:43:43 1997

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