At 06:06 PM 03/06/99 -0300, you wrote:
>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!).
What I had in mind as "semi-automatic" is less automatic than your
approach. It would locate all LD (x000h),A instructions, dump the bytes
around it to your screen and then ask you "modify yes/no?". Usually, by
looking at the bytes surrounding the "32 00 x0", it's easy to judge whether
it's code or data.
>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 seen some cracks that used the upper 64K of VRAM to store blocks
when they were not used. Many older Konami MegaROMs use only 64K of VRAM
(or 16K if they're MSX1 games).
But many of those 128K cracks had bugs (Vampire Killer, King's Valley) or
slowdowns (Firebird). I think Maze of Galious did run fine, though.
>> 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".
By writing to a certain bit.
>From memory (could be incorrect), it's #7FFE, bit 4.
In "write enable mode" you can access the SRAM like normal RAM (except for
address #7FFE and #7FFF). Page switching does not occur if you write at
#5000, #7000 etc.
In "block select mode" it behaves as ROM and you can select pages as usual.
>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.
Impressive!
Konami also did such a thing, on Game Collection 3, but ofcourse they had
the source codes available to them, making it a lot easier.
Martos did a lot of re-arranging on Solid Snake. He made a kind of
mini-BIOS, so that game routines could be fitted into #0000-#3FFF area.
>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.
Not all address based FDCs are equal. The one in the Philips machines is
similar to the one in the SONY machines, but for example the turbo R FDC is
very different.
Bye,
Maarten
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