The Bittboy and Pocket-Go both have a problem with VERY slow fscks on large FAT32 partitions, see this post for details: http://boards.dingoonity.org/other-game-systems/bittboy-cfw-guide-v1-v2/msg188692/#msg188692
. The tldr of that problem is you can expect to wait up to 5 minutes+ for your device to boot under certain circumstances. By the time it boots, you don't have time to play any more!
I have found a workaround - leave the FAT32 part small and use the EXT4 part for bulk storage.
2. DD latets Bittboy/Pocket-Go CFW image to SD card
3. sudo apt update && sudo apt install gparted -y
4. sudo gparted
5. Unmount all partitions
6. Move the FAT32 partition all the way to the end of the drive and expand it to 2048 MiB
7. Move the linux-swap partition all the way to the right
8. Expand the rootfs partition to fill the remaining space on the card
9. sudo mkdir /media/YOUR_SD_NAME_HERE/00-roms or similar
10. Fill 00-roms with your roms. (shotgun chmod/chown stuff, use sudo etc if you have problems)
11. In Gmenu, press select on each emulator and point the file browser to the correct folder.
Using this setup, I arrive at GMenu 20 seconds after boot, even with a 400 GB card and after a dirty power cycle. I find this boot time acceptable.
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(not added megaCD and TG16-CD sets yet, still sorting)