Sega CD conversions

[atom]

I didnt even think about mirroring. Yeah, the other side has its own Motorola as well and some unkown to me soundchip for the cd audio. I still think it will be a stretch, but the Non cd side is def possible (as the SNES was) but It would probably be HELLISHLY slow like the SNES emulator. As far as emulating the CD Your talk about emulating dual CPU's that are completely independent of each other and simply share a data bus meant for a rom. There is also a whole whopping MB of memory on that side and having to hold the ROM in memory. Im assuming the 600MB Cd's would simply be read off the actual cd by swapping lol.

[timofonic]

http://www.eidolons-inn.net/tiki-index.php...egaCD+Multibios

http://forums.segaxtreme.net/index.php?showtopic=11082

Here is the reply from ExCyber:

I don't actually have the patch anymore, but how it works is that
there is a byte-wide "version" register located at $A10001, the upper
two bits of this register are the 50Hz/60Hz flag and the
foreign/domestic flag. The foreign/domestic flag is set to 0 for
Japanese systems and 1 for non-Japanese systems, the 50/60Hz flag is
set to 0 for 60Hz and 1 for 50Hz, so there are four possible
combinations:

00: Japan

01: Japan 50Hz (as far as I know no stock Genesis/MD comes in this
condition, though you could set it this way with a switch, and some
emulators support it as a manual override)

10: North America (possibly Brazil also)

11: Europe / PAL regions

So grab your favorite 68K disassembler (I used Antiriad's DOS port of
the Intelligent Reassembler, which you can get at
http://www.rainemu.com/romerror/ ), look for code that checks the high
bits of $A10001 (the low bits are checked in boot code, you need to
leave that alone or it probably won't boot on some systems), and then
patch the routine to jump/not jump unconditionally to the correct code
path considering the native region of the BIOS and the register
contents it expects (if memory serves the opcode for an unconditional
branch is 60xx as opposed to 66xx or 67xx for beq/bne, and nop is
4E71),

Hope this helps.

[timofonic]

What about dumping the rom from the "cross products" segacd SDK machine?

[Guest]

Get a converter. They're a lot less ubiquitous lately for some reason. I love mine. It's called a "CD+ Plus," which I guess makes it . . . a CD Plus Plus? Just be patient and keep scanning ebay, they keep popping up.

Edit--Here's a link to the store that sold mine on ebay, it's been a while and I'm not sure if the item is still in my ebay list so I don't recall the seller's ID on ebay but if you brush up on your Berlitz Spanish you could probably just order it from their page.

Edit Edit--Found his ebay id, it's armyx.

These converters also will not work for every game. Besides there are multiple revisions of these cd+ carts.

[Endymion]

What game or games haven't they worked with? I haven't run into one yet, although I do use it mostly these days to run my SegaCD games on my Japanese Wondermega 2.

[Guest]

Using revision 1.8i of the cdx plus cart I can confirm the following from firsthand experience:

On a Sega CD:

Earthworm Jim S.E. PAL does not run.

Besides this game I have encountered at least one more (an US one not working on a Euro machine), but I don't remember as I had a very strange Sega CD setup at that time. I had a broken Sega CD and a Mega CD (Euro) and would switch the mobo to play different regions and this has muddled my memory. However most old games (games released before the cart revision) work fine. If you want to go by the experience of others there is a small list of other games that do not work in a Gamefaqs FAQ.
http://www.gamefaqs.com/console/segacd/game/916395.html (the import games one)

(Japanese games)
"Known NOT to work with CD+PLUS:
Black Hole Assault
Heavy Nova

Known NOT to work with Pro CD-X:
Ranma 1/2"

and

http://forums.segaxtreme.net/index.php?showtopic=8683&hl=
http://forums.segaxtreme.net/index.php?showtopic=811&hl=

[wasabisabi]

This question is probably remotely related to the conversions topic but I have been looking for an answer for the longest time. I'll be eternally grateful if someone can answer it for me. Can someone please tell me how I can play US Sega CD/Euro Mega CD games on a Japanese JVC Wondermega RG-B1?
Thank you soooooooo much for your help.

[kendrick]

W, you mean the RG-M1, with the six buttons on top and the keyboard port, right? As far as I can tell there's no model number RG-B1.

For complete import conversion, it'll require a BIOS swap. If you don't have a convertor cartridge that works on a JPN-region console, then you'll have you find yourself a PCB-mount ROM chip and burn a compatible ROM image on it. Since there's so much code that goes into the region checking, there is no jumper to change since the code for running other regions' games simply isn't present in an unmodded Wondermega or Mega CD. Have a look at D-Lite's first post in this thread for a description of how this mod would theoretically be done for the CDX.

-KKC, attaching things to his Xbox 360 that should never be attached to it

[Guest]

THank you so much for the quick reply. Unfortunately, I don't have the technical knowledge so I don't quite understand you method. Do you know of any conversion cartridge, for instance, the CD+plus, CDX or Pro CD that would work on the wondermega model 1? I've read somewhere that it would not because it does the cartridges do not read the code on wondermega. not sure what that means though. please advice.  

[kendrick]

W, please read the thread thoroughly. In order to use a CDX or other convertor cartridge, you'll probably have to do the import jumper mod for the cartridge side of the Wondermega. This is because those cartridges are intended for use in EU and US regions in most cases. This mod process is pretty well documented here on GamesX:

http://www.gamesx.com/importmod/gen2import.htm

-KKC, imagining Lawrence's ears flying off his head. For the usual reason. :)

[l_oliveira]

Old, but very interesting thread. Since I own a japanese (nope actually it's a southern asia unit, the "PAL-Compatible" one with the 9112 bios) I'll share what I know about this stuff...

Due to the crap of SEGA vs. Accolade in late 1990 the second generation of MD Mark I chipset came with a mini bios (SEGA call it IPL or Initial Program Loader) they started to put codes to "protect" the boot of their machines. The idea is make that code copyrighted so if you make discs or cartridges that boot on their system without a licence makes you suitable to a lawsuit from them.

This happen to be a good way to enforce a region protection on the discs. So each region of disc has a boot sector "key" which is actually the code that prints the Sonic and the stars on Euro-PAL/NTSC-US Sega/Mega CD units. The japanese just have a plain blue SEGA logo and the words "Produced by or under licence of Kabushiki Kaisha SEGA".   Since the japanese code has no spiffy Sonic logo (man how I hate that logo lol) it's way much smaller than the Euro and US codes. US code is the biggest one.

What I do is replace the US code with the Japanese one and pad the difference with 68000 NOP instructions so the boot sector is still aligned.
I use CDRWin to dump only the 1st sector, hexa edit it with winhex and then inject the edited bootsector with the same tool used to inject the Dreamcast boot sector on CDR isos (IPINSERT.EXE/IPINS.EXE)

One of the very first games I did this was Snatcher in 2002. I got it on the net, fixed the audio (was off sync due to gaps inserted by crappy dumping programs) then patched the boot sector.

This has a 99.9% sucess rate converting USA games to Japan. The other way arround is not possible at most times because the boot code can't be relocated properly because the japanese boot code being smaller than the code you need to boot the disc on a US or EU SCD.


Peace ...