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Genesis repros don't work (Red Screen)
http://forums.nesdev.com/viewtopic.php?f=28&t=15163
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Author:  lemonpotato [ Sun Nov 27, 2016 12:26 pm ]
Post subject:  Genesis repros don't work (Red Screen)

I tried to do a Mega Man Wily Wars repro by using a College Football's National Championship donor cartridge.

I downloaded a Mega Man Wily Wars .md ROM, used GQ USB Programmer for the Byte Swap, saved the .bin file separately and wrote it onto a 27C160 EPROM.
I also used the tool FixCheckSum before writing the EPROM, as (for some reason) the checksum is always incorrect after byteswapping.

However, when I try to launch the game in my Mega Drive, I only see a red screen. I have no clue what could be wrong, as there isn't any wiring needed.

Does anyone have an idea?

Author:  Fisher [ Mon Nov 28, 2016 3:58 pm ]
Post subject:  Re: Genesis repros don't work (Red Screen)

Well, red screens means checksum errors that are usually caused by bad contact on dirty connectors.

I had the same problem recently on a Megadrive repro I've made and it was one of the data lines that had a bad soldering on it. Specifically it was D12, but can be any other in your case.

Does the byteswapped file run on an emulator? You may try to write it without byteswap, if possible in the same IC.
You can take a look on the file you intend to write on a hex editor, starting at offset 0x100 it should say something like "SEGA MEGA DRIVE" followed by some licensing information.

I'm not sure, but the checksum errors after byteswapping could mean that you don't need byteswapping at all.

Author:  icemanxp300 [ Thu Dec 08, 2016 8:45 pm ]
Post subject:  Re: Genesis repros don't work (Red Screen)

Don't fix the checksum on byte swap. Take a clean rom and open in the programmer, hit byte swap in the programmer and then write. That is all you need to do. You are over thinking it and causing yourself problems.

Author:  Markfrizb [ Fri Dec 09, 2016 8:54 am ]
Post subject:  Re: Genesis repros don't work (Red Screen)

You could use this pcb https://www.mortoffgames.com/sega-genes ... game-board for repos where you don't have to byte swap the rom files.

Edit: I meant you could use this pcb as a non-byte swap alternative. Since this pcb doesn't have sram, it would not be the ideal choice for MMWW.
A fully assembled SRAM version (less the rom of course) pcb will be available in the near future though.

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