From: David Wood (jbevren_at_starbase.globalpc.net)
Date: 2003-03-21 06:36:04
Pretty much, yeah.
It's common, at least in the realm of the Sega Genesis, to mixmatch data
lines to either make it hard to read the physical rom chip on an erpom
reader (to copy to pc), or to make cartridge design simplified.
It doesnt matter if d5 is hooked to d0 on the c64, as long as you put the d0
bits in d5 on the rom when you burn it. The same applies with the adress
bits. What matters is if, in the long run, the bits look to be in the
correct location as far as the target system can see.
-David
On Fri, 21 Mar 2003, Brian Ketterling wrote:
> >From: David Wood <jbevren@starbase.globalpc.net>
> >
> > > either the pinout above is wrong, or Viza intentionally jumbled up
> > > the lines (maybe as a scheme to keep people from reading/copying
> > > the ROM?).
> >
> > ..or they laid it out in this manner to make it easier to design the
> >cartridge (no crossed wires or vias, for example). Either possibility
> >isnt all that uncommon.
>
> Humm... so one views the cartridge as a black box? That is, it doesn't
> matter if externally-consecutive addresses are in fact scattered internally
> throughout the EPROM, so long as a unique address on the buss accesses a
> unique location? And the same for the order of the data bits? ( sorry if
> this is elementary :-)
>
> Is there some way to defeat the cartridge's autostart feature so that I can
> read (PEEK/LDA) and dump the EPROM? My version of Vizastar is XL4, I know
> someone who has XL8, I'm interested in seeing if I can upgrade mine, and
> he'd like to make a copy of his.
>
> Thanks,
> Brian
>
>
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