This venerable line of Dr. Rhythm machines began back in 1979 with the Boss DR-55.
I believe that Roland (the parent of Boss) haven't finished with this line yet.
The history so far of the Boss Dr. Rhythm is thus:
1979 - Dr 55
1983 - Dr 110 Dr.Rhythm Graphic
1986 - DR-220A Dr Rhythm (Acoustic)
1986 - DR-220E Dr Rhythm (Electronic)
1990 - DR550 Dr Rhythm (Mk I)
1992 - DR550 MkII Dr Rhythm
1992 - DR-660 (DR Rhythm)
1993 - DR 5 - Dr Rhythm section
1998 - DR-202 (Dr Groove)
1999 - DR770 Dr Rhythm
2003 - DR-3 Dr, Rhythm
2004 - DR-880 Dr Rhythm.
Sadly the display on the 670 is not backlit.making the screen a little hard to see in dark environments.
There's a good range of drum kits (255 drum & 64 user kits) and percussion & bass sounds
200 preset rhythm patterns and 200 user-programmable patterns.
Preset and User patterns can be easily chained together to create up to 100 Songs
There are 16 distinct sounds including Finger Bass, Slap Bass, Acoustic Bass, Pick Bass.
I think the sounds are pretty sweet though the bass sounds are a little limited and I feel that the hi hat and cymbals lack that certain mojo.But you can edit and change their parameters....pitch, decay, volume, etc.
You can also map different sounds to different buttons.
Midi In & Out.