Japanese BIOS v2.1 Possible [Solved]

[segamemister]

i cant get this to work i know you need to patch it and remove a cartridge check

Did some digging into the disassembly of the Japanese v2.1 ROM, turns out the cartridge detection code incorrectly detects a cartridge, hence why the demo screen never shows up.

A quick hack you can do to make it work on MiSTer is to open the ROM in a hex editor and change the byte at address 0x0118 to C9. This bypasses the cart detection routine completely.

using hxd i cant find the address 0x0118 using the official bios

[MostroW]

I took a look at the v2.1 ROM and the offset you mentioned is not the offset that worked, because address 00000118 is the start of a sub function that is used by the function that checks for the cartridge presence and inserting C9 (RET) makes it return early but does not produce the desired result, which is the cartridgeless BIOS screen that plays the Space Harrier song.

Instead i replaced the instruction at 00000104: CD 26 C7 CALL C726h with 00 NOP and that skips the sub function and starts the no cartridge present function.

TL;DR;
In short, fire up your hex editor and go to 00000104 and replace CD 26 C7 with 00 00 00 and save, this worked for me on the kega fusion emulator and it works on the MiSTer core as well.

Let me know if it did or did not work out for you, if it's the latter i'll take a look again.

[segamemister]

that worked mister wise sincerely thank you!

[MostroW]

good to hear and you're welcome!

[kathleen]

Tested on my side as well on Mister and after the modification it works !
Thanks a lot @MostroW

[MostroW]

Always nice to help out where i can! Enjoy @Kathleen

[8678d]

I was a bit depressed that the Mark 3 core can't show up Turn Off screen.
And It works!! Thank you, @MostroW
Finally, I can enjoy awesome BIOS screen.

[MostroW]

Nice to hear you're enjoying this, enjoy the awesome tune!