blocksize is the dsp vector size, also controlls the temporal resolution of messages... ie. your midi messages can only be processed on block boundaries. Midi having a clock with 1 ms resolution means you want a small blocksize to match. bs = 64 => ~1.4 ms resolution which is decent.
frags is latency... i.e. the number of blocks of lag. IMHO its better to have more frags than a large blocksize.
My laptop has a i8x0 sound card built in that I'm using. For MIDI I use the serial port and a MIDIator 124W. I have lowlatency patches applied to a 2.4.18 kernel, and am using ALSA 9b10. Thanks for any and all help.
I have an i8x0 sound card in a laptop as well (tosh portege 3440ct) and with lowlat patch and alsa 0.9b. Basically the card sucks. In full duplex its impossible to to run with less than 15 ms latency... i.e. blocksize 64, 10 frags. However if I disable the dac or the adc (-nodac or -noadc) then I can get it down to 1.5-3 ms latency.... but usually that's not desirable. I'm certain its a fundamental limitation of the card. Someday we will get a decent USB or pcmcia sound solution for linux and everyone with a laptop will rejoice.
andy