Re: PET 2001/2001N can "write" to ROMs

Am Dienstag, 23. April 2019, 22:13:22 CEST schrieb Mia Magnusson:
> Den Tue, 23 Apr 2019 06:22:33 +0200 skrev Gerrit Heitsch
>
> <gerrit_at_laosinh.s.bawue.de>:
> > On 4/22/19 10:14 PM, Francesco Messineo wrote:
> > > Hi all,
> > > Ok, the subject is a pun, but write is in double quotes anyway. I
> > > was wondering why the PET (at least the 2001 and 2001N, the ones I
> > > have), leave the ROMs selected during a write cycle on ROM space.
> > > This of course makes a data bus contention because the selected ROM
> > > will drive the data bus and the 6502 will drive the data bus too
> > > since it's on a write cycle.
> > > I wonder if this can be a factor in the high failure rate of the old
> > > 6540s and the newer 2332/2316.
> >
> > No, NMOS outputs cannot be damaged if they work against each other.
>
> Somewhere I read about copy protections for C64+1541 that let the 1541
> write to ROM more or less contiguously if the software thought it was a
> pirate copy, and this apparently damaged the ROMs.
>
> Not sure which process those ROMs were made of though.

that sure sounds like an urban myth. you can "write to ROMs" as much and as
long as you want :)


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