[LAD] JACK and ALSA elucidations

Hi LADs We are working on an ARM based MOD device and while fiddling with JACK some questions appeared. I didn't know whether to post on the ALSA os JACK lists, so I decided to post here :-) When I start Jack in my PC I get the well know message: /usr/bin/jackd -P80 -dalsa -r48000 -p128 -n2 -D -Chw:0 -Phw:0 creating alsa driver ... hw:0|hw:0|128|2|48000|0|0|nomon|swmeter|-|32bit configuring for 48000Hz, period = 128 frames (2.7 ms), buffer = 2 periods ALSA: final selected sample format for capture: 32bit integer little-endian ALSA: use 2 periods for capture ALSA: final selected sample format for playback: 32bit integer little-endian ALSA: use 2 periods for playback When starting it on the Beaglebone Black I get: /usr/bin/jackd --realtime -P80 -dalsa -r48000 -p128 -n2 -Xraw creating alsa driver ... hw:0|hw:0|128|2|48000|0|0|nomon|swmeter|-|32bit configuring for 48000Hz, period = 128 frames (2.7 ms), buffer = 2 periods ALSA: final selected sample format for capture: 32bit integer little-endian ALSA: use 16 periods for capture ALSA: final selected sample format for playback: 32bit integer little-endian ALSA: use 16 periods for playback - what are those "periods" in the ALSA lines? (2 for the PC and 16 for the BBB) ? I read a post by Jeremy Jongepier about the Cubieboard2 stating that the hardcoded values for the Cubie (Minimum number of periods was 4 and minimum buffer size was 1024) where unfit for realtime operation. Why is that so? - on the ArchWiki page on Jack there is a D-bus call jack_control eps realtime true stating that it "Sets JACK to realtime mode in its own internal setup." What is this internal setup? How do I address this when not using D-Bus? King regards all Gianfranco Ceccolini The MOD Team PS: We will be at LAC againd this year. I'm very eager to meet most of this distinguished community members there. We have lots of good new for the MOD in 2014.