RE: Ribbon Cable

Yeah the problem we had with Magic Voice was it would take over the bus
when the 6502 went for the reset vector at $FFFC and would take over the
boot.  The problem we had was we had to do some housekeeping to set up the
MMU/VIC first but couldn't really stop the MV cart from jumping in.  To
get by it we inverted the reset line and made the Z80 wake up first and
set up the MMU for C64 mode if it saw a C64 cart, and then start the 02.

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Groepaz
Sent: Tuesday, December 17, 2013 5:23 PM
To: cbm-hackers@musoftware.de
Subject: Re: Ribbon Cable

On Tuesday 17 December 2013, you wrote:
> and that some carts
> like the Magic Voice cart would drive the bus at unexpected times
> including the high address lines (They would toggle /GAME and /EXROM
> dynamically when the system had been designed for them to be solder
> jumpers).  Eventually I stopped trying to "improve" it and try to
> learn to "live with" it.

its a common trick used by a bunch of cartridges... for example to switch
to ultimax mode depending on the address lines, so you can get memory at
8000 which can accept writes.

magic voice is interesting though, as the software first probes the
cartridge in the passthrough port, and then sets its own game/exrom lines
accordingly ... would make an excellent cartridge dumping setup with a
little bit of custom software :)

-- 

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the same reason.


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