Re: [stella] Dumping ROM images

Subject: Re: [stella] Dumping ROM images
From: "Russell Babylon" <rbabylon@xxxxxxxxxxxx>
Date: Sun, 13 Mar 2005 07:01:54 -0500
It will work with bank switch games at least for the 'simple' bank switching
schemes.   As I said in my original message, and you alluded to below, I
dumped an 8K game.  I did not mention that I had some LEDs hooked to the
data lines so I could literally see what data was being accessed in the ROM
and I had a pot for the timing resistor on the 555.  I would set the pot to
a high resistance so it was clocking at a verrrry slow speed.  Sometimes the
ROM would power up in bank one and sometimes in bank two.  I read each bank
out separately and then made a quess as to which one was bank one and
concatenanted the second file to the first.  I believe the data after the
hot spots in the ROM was the same for both banks, even if it wasn't you
could manually edit the few remaining bytes if need be.  Thinking about it
the vectors after the hot spot would have to be the same, at least for the
start up address, if the ROM was to power up consistently.  As I said
originally this was a very simple method that required a fair amount of
knowlege as to the nature of the ROMs and their data structure.  It was not
a plug and chug.

----- Original Message ----- 
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
To: <stella@xxxxxxxxxxxxxxxxxx>
Sent: Saturday, March 12, 2005 6:05 AM
Subject: Re: [stella] Dumping ROM images

> >I say to keep things simple.  Several years ago I made a cart reader from
> > 555, three 7LS161's and a 7400 NAND gate chip.  I connected this to the
> > parallel port of a PC and wrote some code using QBASIC, hey it was what
> > had.  The 555 was set up as a one shot and was reset from one of the
> > signal
> > lines from the PC port, this was how I synced the PC to the cart reader.
> > Using this I ws able to dump the ROMs for Sir Lancelot and Moon Sweeper.
> > At
> > the time the ROM image floating around for Moon Sweeper was only 4K, it
> > a
> > 8K game and some folks were looking for Sir Lancelot.  I can't remember
> > the
> > details, I will have to check my old PC to see if the program is still
> > it.  It was nothing fancy but it worked.
> Unfortunately that's a bit too simple for bankswitched games.
> With this method you would always access all bankswitching
> hotspots in a row. So the data after the hotspot addresses will
> always be read from the last bank. In fact we had to add a special
> bankswitching mode to z26, because people kept complaining about
> these two ROMs. ;-) The games couldn't be started in the first bank,
> because the system vectors were read from the second bank. So we
> had to add a special bankswitching mode for these two F8 games
> were the game gets started in the second bank.
> Ciao, Eckhard Stolberg
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