I backed up the firmware from a special MSX ROM cartridge titled `ちゃっかりCOPY` and sub-titled `カラースクリーンコピーソフト` (Chakkari Copy: Color Screen Copy Soft) by Epson. Apparently my Epson Chakkari Copy has a newer/more bugfixed BIOS than the version openMSX knows about - for instance it correctly spells `illegal` in a couple error messages that were previously mis-typed.

ROM fingerprint info:
```
8.0K Chakkari Copy - Color Screen Copy Soft (Epson) (Japan) [a] [_].rom crc32:a87ed3a4 md5:a8a2d08d0c5e9ee59172ab4ed68a71e9 sha1:aa45362b4ea7c7274e4988966bd08e114e56d04a sha256:c60c4edca950b04e1adaa04f6e8f21c10145045fc55923bff0acfe169b36ab4a size:8192
```
