Region free BIOS for MEGA-CD Version 2.00

One more happy user. Thanks a lot, l_oliveira
Coming soon: A REAL and TECHNICAL method of adjusting the (insert expletive here) pot of the optical pickup. I had to do it on mine, and discovered wonders.

 

The JVC X'eye uses a SOP40 chip for BIOS. Any recommendations for which particular SMD Chip I should use as a replacement?

 

Quick question for the knowledgable, does it matter which region Mega Drive or Genesis is installed onto the CD unit with one of these region-free BIOS files?

 

It does, based on the version/type of CDC (CD controller aka CD drive MCU). MEGA-CD 1 units can only have SONY (SONY KSK-1200) or Hitachi (JVC drive) CDC.
For MEGA-CD 2 units there are also a new kind of CDC chip from NEC. There are a variation of BIOS which only works on those (the service manuals refer to that board type as the "FUNAI UNIT").

Also keep in mind that WONDERMEGA2/X'Eye units are a lot different from other MEGA-CD units and while it's BIOSES may boot on a CD2 "FUNAI UNIT" board, there will be problems with the CD-DA muting switch (you have no CD-DA muting control) so it will cause you to have no CD-DA audio.

So to "KISS" (Keep It Stupid Simple) you are free to use any regional variations as long you stick to BIOSes which are right for the hardware version you are using.


FYI, KEGA FUSION emulates a CD1 unit with SONY CDC. BIOSES intended for the FUNAI UNIT board fail on it the very same way they do on a real CD1 unit.

 

No Shane it doesn't matter.Japanese on US system, or Japanese on Pal, all works fine. Just has to match the system, 2.0 on tooloader etc.You can test this before installing it by using an everdrive.

 

By the way, you know if krikzz fixed that silly everdrive problem with the programmable interrupt pointer (for split screen stuff) that MEGA-CD has?

That caused glitches on SNATCHER (text disappearing) and made Silpheed crash at Game Arts logo if EVERDRIVE was used for loading the CD BIOS.

 

i have no clue, i run a region free mega cd bios so i never use it to play games with bioses loaded form the Everdrive. only use ti to play the US version of flashback since it detects non US bios and halts.

 

Thanks @l_oliveira and @skyway1985
I guess I was a little confused at the jp_mcd1_911228_pal_regfree file, was there a reason PAL gets a different BIOS? jp_mcd1_911228_regfree would do the job wouldn't it?

Also I have a Mega EverDrive and a Mega CD here, want me to test it out? Any BIOS in particular?

 

Asia BIOS serves HK and due to UK former influence they happen to use 50Hz TVs there so the ASIA BIOS only enforce DOMESTIC check and will work properly as is on 50 and 60Hz systems. Japan BIOS is 60Hz only and will glitch at 50Hz with the lock removed.


Edit: Everdrive will glitch any BIOS you try, including non modded ones as the reason for the problem is hardware not software. (a register from MEGA-CD ASIC chip is masked out)

 

Perfect, thanks for the explanation! And thanks again for patching these

 

Howdy @l_oliveira any chance of getting this one spliced up with your region-free goodness? I was reading one of your posts over at Sega-16 and noticed you hadn't seen this particular version yet. It does seem to have made its way into no-intro though now.

jp_mcd1_911120 (EPR-14088B).bin

Pretty please?

 

Absolutely. Will download it and try right now.

 

There you go, my good sir.

 

Thanks a million! You are the best!

 

Would I be able to submit translations for the Mega-CD BIOS, or would you be able to do that yourself?

(and maybe, if you're using them, the decompiled/uncompiled bios file code.)

 

Oooh, having the Asian BIOS in English would be very nice indeed.

 

hi there, i've got one of those jp regionfree bios for my european megacd2 (eeprom 24c1024supplied by bad-ad) and can't get it to work, i'd like to have it piggybacked with the original eur bios in place. are there any tutorials to follow? (i followed a tuto on youtube SEGA CD 2 Region-free BIOS mod (Original+hacked on 2-way switch) ... ) but without soldering the back row of the eeprom seems to me a bit unstable, tried it and it's not working (switch on original bios still works, but new one gives black screen). thanks!!!

 

Take the file you wrote to the eprom and try to use it on a emulator. If it works on a emulator it needs to be byte swapped. The MC68000 is a big endian CPU which means the data is stored "backwards" on what Intel CPUs expect (I.E.: Windows PC) and since you're trying to use the file on the real thing, it must be "un-swapped" as the file is swapped to be readable on Intel PCs. Basically you need to byteswap before writing to the chip.

 

He didn't write the file, I did.

It's swapped correctly.

Need pics of what you have done for the piggyback. As you need some pull up/down resistors to do a piggyback install and lift a pin

 

Even if he were using the wrong BIOS for his unit he would get at least the space/sky/background screen. Black screen means something is wrong with the BIOS. (bad checksum, for example or it didn't even start to run. Unlike games, MEGA-CD BIOS don't turn the screen red when CRC fails. It just sits on a idle loop.)