Re: [LAD] audio/midi app development

On Wednesday 16 June 2010, Patrick Shirkey wrote: One of the test tools that might be enlightening for the MIDI folks here, is the machine control program called emc. Because jitter is very important when feeding a stepper motor controller a steady heartbeat at high audio and somewhat above frequencies, the coders have developed a 'latency-test' script, which you run on one screen, then abuse the heck out of the machine doing other things, (browsing the web, moving windows around, compiling a kernel, whatever warms up the cpu) then come back half an hour or more later and read the average and worst case latencies as displayed in nanoseconds. Those are generally big figures so do the math and make milliseconds out of them. Emc when running stepper motors is fussier that all get out, and that tool just might point the finger at truly bad motherboard, or video hardware. FWIW, an nvida video card, can only be used in a machine running emc if the vesa driver is selected, all the others including nv, tie up the interrupts, sometimes for many milliseconds. For emc, that would equal a stalled motor and a wrecked part you were cutting at the time it stalled. Similar things can be said about the APCI of some motherboards. If that can't be fixed via a bios setting, toss the board. Via chipsets seem to be the most popular in this latter category. If its a complex part that you've already got several hours worth of carving & cutting tool wear into, that will only happen once, because whatever the culprit is, gets both found and a free airmail trip into the bin. What? Oh, I'll go back to lurking now. ;-)