On Wed, 10 Mar 1999, Maarten ter Huurne wrote:
> At 09:58 AM 3/10/99 -0300, you wrote:
>
> >That's ok for Konami, Compile and T&E Soft games, but there are some
> >strange ones that does use other ways of block switching. BTW, T&E does
> >use very often LD HL,0302h / LD (9FFFh),HL
>
> Hmmm, ROMs like that would be difficult to adapt for ESE-SCC.
> MegaRAM does allow such a page switch, right?
Yes, Megaram accepts the block number in every memory position within the
addressable area of the block. LD (4000h),A and LD (5FFFh),A have the same
effect (after a OUT (8Eh),A ). This happened exactly because Megaram was
designed to simulate perfectly the most part of the Megarom games. After
that, a few softwares were designed to take profit from that.
> >I had saw in Nemesis x, F1 Spirit and Penguin Adventure that Konami, at
> >each interrupt, changes blocks 1, 2 and 3 to 13, 14 and 15, respectively
> >at positions 6000h, 8000h and A000h.
>
> A crack could group blocks like this: 0 and 1, 2 and 3, 0 and 13, 14 and
> 15. 8K is "lost" because block 0 is duplicated. But switching is very
> efficient: two blocks can be switched using a single OUT to the mapper.
> Ofcouse blocks visited as frequently as these were never put in VRAM.
That's explained why 128kb Megarom games cracked requires 256kb of Memory
Mapper. I remember that, when I converted the Mapper version of R-TYPE to
proper operation with Megaram, I found a "priorities table", because it
uses the VRAM to store some blocks. And the most accessed blocks were
stored in the Mapper. But that's a 256kb game, isn't it?
> >I didn't know that the DSK version was adapted to run with only 256kb of
> >Memory Mapper! What was more difficult: translate do English or adapt do
> >256kb of Mapper?
>
> I can't say, because it was not me but Martos who did the 256K version. The
> only thing I did to it was fix a bug in the load routines. Before the bug
> was fixed the 256K version crashed quite often.
> The 256K version is without sound however, so it is not equal to the 512K
> version.
Why this conversion cut the sound? Did it cut the PSG sound?
> >But, with direct access to FDC, the data transfer rate is maximized. And
> >the main idea was copy protection, using special formatting (1kb sectors)!
>
> Why use copy protection on cracked games? Isn't the whole point of a
> cracked game that you don't have to buy it?
Well, that's a long story. The Nemesis conversion wasn't made by me, and
it was the first and the best conversion made in Brazil. In that time, the
copy protection technique was so advanced (compared with the knowledge
available) that absolutely nobody could copy it. So, the guy that made the
conversion had really made some money from that. I tried to do the same,
but 1 year after his conversion, people discovered that PC's could copy
the disks with that copy protection, and then he almost stopped to make
money with that project. So, he never made another Konami conversion.
My conversions (like Super Laydock, Mirai, Fantasy Zone, Young Sherlock,
Final Zone) were made 3 or 4 years later than Nemesis conversion, and I
had made absolutely no money, because in that time copier software had
already existed. So, I made a research of all the capabilities of copy of
that softwares, and I had created a new kind of copy protection. Some
months later, another guy created a new software for special disk copies,
and that copied several times my conversions.
It was very impressive the way how my conversions had been spread over the
country, after 3 months all brazilian magazines were announcing people
selling copies of my conversions of Megarom games.
> By the way, 1K sectors can be loaded by some diskROMs. 8250 can do it,
> turbo R can't. I was planning to use it as a copy protection as well. But
> because I didn't want to do direct FDC access, I discarded it.
Turbo-R Diskrom can't read 1kb sectors because the way the main reading
loops was made is completely stupid!
LD B,00h
LOOP1: LD A,(07FF4H)
ADD A,A
JP C, LOOP1
ADD A,A
RET P
LD A,(7FF5H)
LD (HL),A
INC HL
DJNZ LOOP1
LOOP2: LD A,(7FF4H)
ADD A,A
JP C,LOOP2
ADD A,A
RET P
LD A,(7FF5H)
LD (HL),A
INC HL
DJNZ LOOP2
And after that, the program sends a cancel command to the FDC. Some time
after I made my conversions, I discovered that the brazilian diskrom could
read 1kb sectors, but that was too late.
Greetings from Brazil!
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Marco Antonio Simon Dal Poz http://www.lsi.usp.br/~mdalpoz
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