[LAU] pc-keyboard with midi game port

[Renato]

Hello, today I found in the dumpster this pc-keyboard which is neither
ps/2 or usb, but has these two connectors which to me seem midi game
and plain midi.

http://imgur.com/1H72s.jpg

I connected the midi plug (purple) to my soundcard but it doesn't seem
to output any midi things (note on, off,cc etc.). Should it and it is
just broken or do these gaming devices use a midi physical port but an
entire different protocol than music-midi?

thanks for any help,
renato