Most Compatible BIOS files for MegaCD Core?

[kikaso]

What are the BIOS files that offer the widest compatibility for each region? (North American, PAL, and Japan market) I've seen several versions for each region.

[JUNKER Seed]

There’s a region free BIOS floating around the Internet. Makes dealing with Sega CD games a bit easier.

[ItalianGrandma]

I just have US , Japan, PAL and region free bios on mine. Region Free seems to work well for most things, but I have heard others say they can cause issues (though, none that I have seen).

[kikaso]

There’s a region free BIOS floating around the Internet. Makes dealing with Sega CD games a bit easier.

Not what I was looking for but damned if it's not what I needed. Thanks!

[Brettster]

I would have thought the older bios would be the most compatible as devs would have had to target that one as they were not upgradeable by the user
The region free ones seem to work ok on the MiSTer, I did have problems getting a Ninja Warriors to run on Megadrive hardware with anything but a Japanese bios though

[kikaso]

I would have thought the older bios would be the most compatible as devs would have had to target that one as they were not upgradeable by the user

That was exactly my thinking.

[Kitrinx]

I can't say which is the most compatible, but two that you should NOT use are wondermega and xeye. Those bioses have some differences that can interfere with the sound.

[kikaso]

I can't say which is the most compatible, but two that you should NOT use are wondermega and xeye. Those bioses have some differences that can interfere with the sound.

Thanks for the tip!

[Lisko]

Also about region free bios, the Japanese one should be the most compatible as some rare Japanese games will check the bios data itself. It's also the recommended one from the region free developer. I suggest the mega cd 2 one because mega cd 1 bios seems to have problems with mister by not correctly detecting tray status if "reboot after inserting" is set to OFF.

[darksakul]

On top of that I seen some Japanese games have visual artifacts (like all the black is replace with hot pink).
I found this out on real hardware and CD rip hacked to boot on a US Bios.
I used a Everdrive to boot the Sega CD with a Japanese Bios.

I use a Region Free Sega CD Model 2 Bios as my Go to with the Japanese as Standby.
(I like to use the Sega CD rom menu and I can't read Japanese).

[kikaso]

I suggest the mega cd 2 one because mega cd 1 bios seems to have problems with mister by not correctly detecting tray status if "reboot after inserting" is set to OFF.

You're right. I think the Sega CD 1 BIOS has that problem too.

I use a Region Free Sega CD Model 2 Bios as my Go to with the Japanese as Standby.
(I like to use the Sega CD rom menu and I can't read Japanese).

That's what I'm doing now after learning about region free BIOS. I have the PAL region free BIOS for only one game; The Smurfs. Coincidentally, the core was just updated to support per game CD BIOS. I know that was requested in another thread.

[pcfreak324]

Is there a Japanese BIOS that autoboots into a game once the disc is inserted (like the US CDX BIOS does)?

[ItalianGrandma]

I would have thought the older bios would be the most compatible as devs would have had to target that one as they were not upgradeable by the user
The region free ones seem to work ok on the MiSTer, I did have problems getting a Ninja Warriors to run on Megadrive hardware with anything but a Japanese bios though

Interesting point I hadn’t thought of!

Ninja Warriors worked fine for me using the US Region Free BIOS, so it’s interesting that your copy didn’t work.

[darksakul]

Is there a Japanese BIOS that autoboots into a game once the disc is inserted (like the US CDX BIOS does)?

Not that I know of on hand, but then again I like to avoid the CDX Bios as it tends to have issues in FPGA devices and emulators.
I like to stick to the Region Free hacked Model 2 BIOS files, even if I am matching that Region with the ISO

For me the Japanese game that had issues was Devastator (all the black in the game appears as hot pink) I would before manually boot the Japanese Bios, but with the recent update I just have a copy of the Bios in a folder with the game.

I would have thought the older bios would be the most compatible as devs would have had to target that one as they were not upgradeable by the user
The region free ones seem to work ok on the MiSTer, I did have problems getting a Ninja Warriors to run on Megadrive hardware with anything but a Japanese bios though

Not exactly, newer versions of the BIOS are often developed to fix errors and flaws with the old code.
It really depends on that particular development and what was their goal with the rewrite.

[eightbit]

Regarding the region free BIOS, I have tried all I could find online and no matter the version, the game loading freezes right after the Sega/Sonic intro right before the game is supposed to launch. Not a big deal as not I have resorted to official BIOSes per game folder (whatever region they need).

But I am just curious as to why the region free BIOS would freeze on game launch? It appears others in this thread are using it just fine...

[Lisko]

Odd, region free bios works fine here.

[eightbit]

Odd, region free bios works fine here.

Yeah, very odd. I figured it would be "easier" and "cleaner" to have one region free BIOS as the default. Theoretically it would have been, but not a single region free BIOS would work. They all initlally acted like they were working, but after that Sonic chime and Sega logo, hard freeze.

Official BIOS's however work fine, all of the revisions I have tried. So, I have the v2.00 USA BIOS as the default and for folders with Europe and Japan titles I have their respective Euro or Japanese BIOS revisions in the game folder(s).

Everything works fine that way, but why the region free BIOS does that for me I have no idea.

[Lisko]

Odd, region free bios works fine here.

Yeah, very odd. I figured it would be "easier" and "cleaner" to have one region free BIOS as the default. Theoretically it would have been, but not a single region free BIOS would work. They all initlally acted like they were working, but after that Sonic chime and Sega logo, hard freeze.

Official BIOS's however work fine, all of the revisions I have tried. So, I have the v2.00 USA BIOS as the default and for folders with Europe and Japan titles I have their respective Euro or Japanese BIOS revisions in the game folder(s).

Everything works fine that way, but why the region free BIOS does that for me I have no idea.

You could try resetting mega cd core settings and temporarily moving saves away. Just to remove all possible variables.

[eightbit]

My issue ended up being incorrect region free BIOS files. The set I obtained were tested on real hardware (from what the readme said) but would freeze on the core. I obtained an alternate set from an unnamed individual (thanks unnamed individual!) and it worked as expected. I had a feeling this was the issue.

[antibolo]

Seems the core now looks for cd_bios.rom recursively down the directories, making it easy to split up your images into directories for each region, with a single cd_bios.rom for each region. That's pretty cool! Even though the region free hacked bioses exist, it feels cooler to see the BIOS of the game's matching region pop up at launch.

[kikaso]

Seems the core now looks for cd_bios.rom recursively down the directories, making it easy to split up your images into directories for each region, with a single cd_bios.rom for each region.

That’s really cool. I’m obsessive enough that now I’ll have to create the region-specific directories.

[ListoMefisto]

Hello eightbit, I have the same problem you had. Can you help me with that alternate set from an unnamed individual? All the free bios I have acted like they were working, but after that Sonic chime and Sega logo, hard freeze.