Re: It's working!

> > In short, I have the mod working! It had two problems:
> Way cool hack, and thanks for the assemblable stuff.

No prob. The Asteroids Deluxe even divorces the code in the vector ROMs

> I, too, am interested. Been a long time since I looked at this.
> I might actually do something worthwhile with it :)

Like program a new game? ;-) That'd be cool.

> Anyone know of any timing-critical stuff in Asteroids? Because
> it's a vector game, we don't have to worry about monitor sync
> frequencies derived off the crystal. Popping in a faster crystal
> might be handy if future software mods require more CPU power.

None of the 3 aforementioned games are time critical inside the code. They
use the fixed rate of the NMI (4ms) to advance things. That's the only
thing that relies on the clock.

However, rather than popping out the crystal, one could just move the
incoming clock on the 6502 to the 3MHz or 6Mhz taps on the 9316 (C3)
counter. That would still allow the NMI and other circuitry to run at a
constant rate regardless of the CPU speed. The foreground code in all the
games spins on a semaphore set by the NMI. Of course the vector generator
can't run any faster, but since it's held back by the NMI and the NMI
speed wouldn't change, it'd run fine.

Anyone know of any faster 6502s that run at 6Mhz? Can the RAM keep
up? I'll dig around...

-->Neil

-------------------------------------------------------------------------------
Neil Bradley Play a song wrong once and it's a mistake.
Synthcom Systems, Inc. Play a song wrong twice and it's Jazz.
ICQ #29402898

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Received on Wed Apr 25 17:59:39 2001