I have 4 HDDs here with me, from 3 different manufacturers, and all of them have the following 4-pin extra interface beside the SATA connector:
Looking on internet, I can see that it exists on all HDD devices, but not on SSDs:
On old IDE devices there was a similar interface used to select operational mode(master/slave), but on SATA it doesn't makes sense any more.... So, could someone tell me what this interface is intented to do and why it doesn't exists on SSDs? It is used on any practical situation?