Re: Saturn / Titan Accelerator II

[Michael J. Mahon <mjmahon@aol.com>]

STYNX <stynx@gmx.de> wrote:
> The board has a very tight fit to the connector ;-)
> 
> I have already tried _every_ (binary increment) switch-combination
> with no result (only switch 1 lets the system stop right at the
> beginning - like a never ending system check)
> The real problem is that the board seems to be ok. If it wouldn't work
> at all i could start on the hardware level of just trash it ;). But
> this is so frustrating! Seems like i have to check the signals on the
> board itself with a logic analyzer. There may still be a chip partly
> defective ? (had already to replace some - the ones with black marker
> are new)
> I'm more of a PC/Mac-collector and have just recently found me deep
> interest for _everything_ "vintage technology" (an open-collector - so
> to speak *g*).
> Sadly my understanding of 6502-systems (timing and such) is quite
> limited -- but you always have to start somewhere ;)
> 
> greetings
> -Jonas

I wholeheartedly agree!

As you note, the good news is that the card works at normal speed. 

Because all Apple II accelerators need to run at normal speed for accesses
to certain address ranges, they have a logic signal corresponding to
"acceleration off" (or its inverse).  It seems likely that the decoding
circuitry that asserts this signal is failing. 

Look for chips associated with address decoding for the on-card processor
and the DIP switch.

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon