Should we ask RetroJunkie if we can get this BIOS dumped? We may have a Japanese v2.21 BIOS on our hands here if he can (if he can find one or has one).
I have asian model and Linguaphone model in hand.I may dump them when I'm free to remake the dump cable and find a computer with parallel socket. But personally I think they are exactly the same in binary.Because the asian model multi-mega in my hand is NTSC.So it's 60Hz+Domestic switch.That makes it works identically as Linguaphone. And I'm wondering if there is PAL asian model multi-mega released?Like in HongKong or in somewhere use PAL standard.
I'm looking to sell it so I'd like to keep everything intact for now. It's an absolute nightmare to open truthfully and I don't trust myself with it. Speaking from a previous experience ofcourse.
I recorded the boot animation and cd player UI of my Asian NTSC model Multi-Mega and Japan (NTSC) model Linguaphone/Education Gear. https://www.youtube.com/watch?v=zw00JJDUrrQ For BIOS dump.I found I have already done that 3yrs ago.I will contact redump or no-intro for releasing it properly. For BIOS emulation.Yes,it's not fully supported by Kega just like CDX BIOS.So it will only be useful for CDX region free BIOS mod.
As member @zoinknoise recently contact me for a dump of Linguaphone BIOS for multi region CDX mod. I found I should update this old post: I tried to find the BIOS I dumped and I found a pack file I made early 2012 in my archive HDD with 6 dump results and confirmed it's dumped from my Asian Multi-Mega, not the Linguaphone one. The dump method is using the transfer cable introduced by "https://www.retrodev.com/transfer.html". But sadly I don't have the cable right now to dump the BIOS from Linguaphone, and it's not easy for me to find a computer with parallel port in hand, either. So I suggested @zoinknoise that using the dump from @Bad_Ad84 in another post in Assembler forum(here) as I assumed that the NTSC Asian Multi-Mega is same as Linguaphone in BIOS. @zoinknoise gave me a nice suggestion that I can open the Linguaphone the check if the BIOS chip has the same parts number as Asian Multi-Mega. I think though it's still not accurate but it would be usesul as a reference before I can find time to make dump cable to dump the BIOS itself. So here is the photo of this chip.It seems it's same as the one mentioned by @Bad_Ad84 in the above post: MPR-16822-T. And I found there are 2 bytes difference between my Asian Multi-Mega BIOS dump and @Bad_Ad84's dump. And that makes me doubt if it's accurate to dump BIOS through the transfer cable. The difference is at the offset of 68000 level 4 interrupt autovector(offset 0x70). And as the byte of @Bad_Ad84's dump is same as other Sega/Mega CD and his dump is through programmer.I think my dump is not corrent in this offset(@Bad_Ad84's dump is 0xFFFFFD0C and mine is 0xFFFF0000). I'm not sure if it's caused by my cable or my Multi-Mega. But as 6 dumps result shows same in this offset, I think it's at least not caused by the signal error during transferring.(As one of the dump has another difference byte than the other 5. I think it's not very hard to identify similiar random error during the transferring through the cable.) I left this not here for reference. If anyone dump BIOS from Sega CD related devices, please recheck the value on offset 0x70.
This is a known issue with dumping via cable. It was mentioned on here a while back. I will try and find the thread.
Really thanks for your confirmation. So I will treat it as an improper way or at least a way that need additional fix in future dumping attempt.
I can't seem to find the thread. But from memory it goes like this: The bios is read to memory and that vector is initialised by the bios. But games could change it too if they like. As the bios is read after this has been initialised, it comes through with the dump. The value being there doesn't matter, as it would be overwritten on real hardware anyway. This is paraphrased, from memory. So take with appropriate amount of salt.
I can get it. BootROM changed those byte before loading the transfer program. So even transfer program untouched anything before or during the dumping process. The mapped memory content is already polluted by code of BootROM it self. Thanks a lot.
If the MPR number matches, then the ROM data is a perfect match. That number is the identifier Sega uses for mask roms, there's no way for the dumped data to be any different. If it was EPR or OPR, then it is possible that data was corrupted (those are all PROMs), but with mask roms it is unlikely. Thanks for confirming the BIOS inside those units!
