Author Topic: BUG: ROMs with Short 8.3 FAT32 filenames are always booting in SMS mode  (Read 2304 times)

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Offline Overkill

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I recently picked up an Everdrive GG from Stone Age Gamer. I noticed one major issue with the current version 8 firmware that comes up when running Game Gear roms with short FAT32 filenames (8 characters filename, 3 characters extension, single case), which causes games to launch in the incorrect mode (launching a game as SMS instead of Game Gear).

Steps to Reproduce

1) Provide a game gear ROM which clearly identifies its region code as $5 or $6 in $7FFF of the ROM header, and relies on VDP features to operate in GG mode (12-bit CRAM, etc).
2) Make two versions, one with a 8.3 filename (eg. HELLO.GG or and another with a long filename (Hello These roms should have identical content, just different filenames.
3) Running the version with an 8.3 short filename "HELLO.GG" will launch in Sega Master System mode (scaled screen, messed up colors, other limitations).
4) Running the version with a long filename "Hello" will launch in Game Gear mode (correct screen size, correct colors).

You can clearly see which files are identified as 8.3 vs long filenames in the Everdrive menu interface, because the 8.3 filename is fully uppercase and omits the extension separator.

Code: [Select]
Code: [Select]

Device Info - Incorrect, SMS mode

Hello - Correct, GG mode

It's almost impossible to see the color difference in this photo (The Game Gear has a pretty horrible screen), the correct ROM is blue background with white text, the bad version is yellow text on black background. Still, you can notice the difference in screen size and the pinkish overscan border which indicates SMS mode.

If necessary, I can provide my specific test ROM that proves this problem, but you should be able to do it with any roms. I've also tried it on a number of GG-specific homebrews from SMSpower that worked in emulators but unexpectedly launched in SMS mode instead of Game Gear on the Everdrive - and renaming them to have long filenames turned out to be the fix.

I'd rank this as a fairly critical bug, since people will not be expecting the filename to have any impact on the file's interpretation by the firmware. In the meantime, people can rename files to force long filenames to overcome this problem.

« Last Edit: July 25, 2015, 10:38 PM by Overkill »