On Fri, 5 Mar 1999, Maarten ter Huurne wrote:

> It's pretty easy to adapt a ROM file to work on a different MegaROM type.
> Depending on the ROM, it typically takes 2 to 15 minutes. And that is
> manually in a hex editor, semi-automatic conversion could be much faster.

Semi-automatic conversion is a bit dangerous! Some time ago, I tried to
make the conversion of some MegaROM games to run directly from the disk,
dispensing the using of extra memory (MegaRAM or Memory Mapper). The
technique consists of exchanging LD (x000h),A to CALL F975h and so on. In
F975h I inserted a small routine to load data from disk.

For some games, it really works!!! (And until now I still may have the
conversions, but my disk-drive is broken, so I can't read them now), but
for other games there's a problem: the conversion software can't detect
whether a game area is code or data, and modify some bytes of data,
generating damage to graphics or sound (or even crashing the game!).

BTW, Konami MegaROM games couldn't be converted anyhow, because they do
frequent block switching, what can't be done directly from the disk.

> I have done it several times to run ROMs in my 512K ESE-SCC. ESE-SCC
> hardware is different from MegaRAM, but the principles are the same.

I would like to know more technical details about ESE-SCC, like: how to
switch between "block select mode" and "write enable mode".

> >In Brazil, after Megaram had been released, the Megarom games that had
> >16kb blocks or other different stuff were converted to the Konami style.
> 
> Even better than converting yourself: converted ROMs are already around.

Yes, but I think this can generate a bit of mess.

Here in Brazil, a guy whose name we don't know had made a conversion of
Nemesis I to run directly from disk, without any memory expansion! But
Nemesis I does frequent block switching, and how did he made this
conversion? You wouldn't believe, but he reconstructed the entire game,
joining the routines that were most frequently accessed, reducing the
block switching rate at a minimum!!!!! But, he spent 8 months in this
work. Of course, no other Konami games were converted in Brazil.

I also have this conversion, but, again, my MSX disk-drive is broken. I
don't know why this happened, but the second head can't read the lower
side of the disks. I'll try to get another drive.

BTW, the Nemesis conversion and my MegaROM games conversions (like
Super Laydock, Final Zone, Fantasy Zone, Mirai and Young Sherlock) uses
direct access to the port based FDC, then, it won't work on European MSX.
Sorry! Perhaps, in future, if somebody is interested, I can make a version
for the address bades FDC.

Greetings from Brazil!

-----------------------------------------------------------------
Marco Antonio Simon Dal Poz        http://www.lsi.usp.br/~mdalpoz
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