Hi Bruce, the cmpci cards have the same hardware design error as the older soundblaster cards (eg. SB16/AWE64). The cards lack the ability to generate interrupts on transmit fio empty, and have only one byte of fifo (hmmm.. that should be named register instead of fifo :-).
If you want to drive your external MIDI gear, just use an interface which has a decent MIDI port. In case you do not have the option to fix the hardware, you can work around the defect using a polling driver or (in case of ALSA) use a high (2 kHz) timer frequency instead of the standard 100 Hz. Frank. On Thu, Nov 21, 2002 at 09:42:09PM +0000, Bruce M Beach wrote: > > Hello All > > I'm sending some midi data to synthesizer for playback > and it appears that the fifo /dev/midi (cmpci mpu401 driver) > is not emptying as fast as it should(could), since the play back > is highly irregular. Here are some numbers. > > 1) The timeing slice remains constant at 30 msec +/- 3usec, > timed both at the beginning and end of the loop, > so the irregularities are not due to loop variations. > > 2) A maximum of 64 bytes burst, with around 5 bytes normal > and an average of 1 byte (say) (ie many slices do nothing) > can occur during a slice, the buffer for the driver is > 128 bytes with around a maximum capability of around 116 bytes > transmitted per slice, so the midi channel can easily sustain > the transmission rate at the rate I am sending information. > > 4) System load while the program is running is around 0.1% > > 5) The midi performance remains the same even if I do something > like build the kernel, and untar some package say glibc at > the same time. > > When I say irregular I mean, for instance on a run of 16th notes > the notes will radically speed up and slow down. The notes all > have the correct pitches and voice changes etc. are all happening > correctly. Just this strange tempo problem. > > Any thoughts or suggestions would be welcome. > > Bruce -- +---- --- -- - - - - | Frank van de Pol -o) A-L-S-A | [EMAIL PROTECTED] /\\ Sounds good! | http://www.alsa-project.org _\_v | Linux - Why use Windows if we have doors available?
