2012/3/8 charles green <xxzzb...@yahoo.com>: > cnczone - ive seen that before somehow.
Probably You saw it mentioned in other discussion, where I posted it, but did You read it? I had a link in there that explains Your next question. > the task manager of winxp has a process priority setting, with one of the > choices being 'realtime'. never tried it for anything. but the realtime > mode of operation in linux is still a general hardware timeshare approach, no? No. ..including stuff like keyboard and mouse. Definitely no. I would like to ask someone more knowledgable to explain it more precisely, but the main principle is that with RTAI kernel the tasks are separated - realtime tasks and all the other tasks. Keyboard and mouse are not on realtime, screen output also is not. Also LinuxCNC itself is separated between realtime and non-realtime, like it is shown here: http://linuxcnc.org/images/stories/EMC_Control_LG.gif In theory, if machine runs short on computing power, the mouse and keyboard might stop responding, screen might freeze, but machine will keep on running the motion precisely. And the whole difference from Your examples is that LinuxCNC follows, if it is keeping up to be realtime or if it is falling behind. I seriously doubt that windoze is measuring and checking, if it really meets the requirement for realtime. If LinuxCNC is falling behind, it displays error on the screen about "RTAPI error occured, run Latency test". INI file specifies the length of base thread and servo thread in nanoseconds. And each thread is ran again and again in repetition, so what LinuxCNC does is it takes the actual time, taken to execute the thread last time, and compares it with the specified number in INI file. If the actual time exceeds the requested time, then it triggers the error - machine continues working, but user is alerted that there was an realtime interrupt. Usually the solution is increasing the thread period (especially true for base thread). There is a Latency test application, which runs those 2 threads and measures the timings and shows the maximum deviation in absolute numbers (nanoseconds). And there is one very very nice feature of Linux realtime kernel, which I am sure is not available in windows: isolating CPUs for realtime There is a boot-time parameter "isolcpus" that allows user to isolate certain cores of CPU exclusively to realtime tasks. That is one more thing why I like D510-series ITX boards - it has dualcore Atom CPU and I usually isolate one core to realtime. Reports from other users show that it considerably improves the board's realtime performance (which is good also without this). 2012/3/8 charles green <xxzzb...@yahoo.com>: > no, i was talking about commercial production machining centers, mostly fanuc > based, 15-30yr old vintages. I cannot think of a better candidate for a LinuxCNC retrofit... Viesturs ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
