Question about HP ProDesk 400 G3 MT

There are a total of 3 S-ATA connections, 2 of which are occupied. Most detailed list of specifications: http://www8.hp.com/h20195...

As already answered by cschales, there is still one free connection.

Mounting is more difficult, as there is no holder for a 2.5" SSD in the case (somewhat outmoded in my opinion). So you have to make do with an extra 3.5" frame... although very few of them fit without any problems. I had to make do in some other way and fastened my frame in a makeshift way with cable ties. There are almost no holes for the screws (only mounting guides/"slides"). This is despite the fact that the model is also offered with SSD mounting.

If in doubt, you can always disconnect the optical drive - who needs that anyway? ;)