This shows a latency-histogram for a 1 ms thread running on Xenomai on my recently acquired ITX-board. Note how badly the histogram is approximated by a normal distribution (Gaussians look like parabolas with logarithmic y-scale!). See also Michael's recent RPi data and Kent's Athlon/P4 data. The usual latency-test numbers people report is the maximum latency, … Continue reading Latency Histogram
I tried a number of things that are supposed to improve real-time performance, as described in this forum post. But not much changed. This series of jitter-histograms shows little or no changes: The things I tried are roughly measure first latency histogram 0.png uninstall the package irqbalance using synaptic. reboot. measure 1.png in /etc/default/grub modify … Continue reading Real-Time Tuning
Why bother with these real-time kernels and APIs at all? Isn't timing on a modern PC good enough? Look at this: This histogram shows latency-numbers from the same 1ms thread test run compiled without (red) and with (green) real-time enabled. All the green real-time data clusters around zero +/- 20us. Without real-time enabled the event … Continue reading Why Real-Time?
Recent developments has made it possible to run LinuxCNC on the latest LTS release of Ubuntu. This is experimental work, so not recommended for controlling a real machine just yet. The main obstacle for moving LinuxCNC from 10.04LTS to a more recent distribution has been the RTAI real-time kernel, which has not been kept up-to-date … Continue reading LinuxCNC on Ubuntu 12.04LTS
I've upgraded Ubuntu and EMC2 on the Atom 330 machine I have for controlling the lathe. The Atom 330 is a dual-core chip, but with Hyper Threading the OS can see four cores. That's not good for real-time performance, so the first thing I did was turn off HT from the BIOS. Next I did … Continue reading EMC2 upgrade
I put together this small computer which will be used to control the lathe. The components for this kind of box are quite inexpensive: D945GCLF2 motherboard including 1.6 GHz Atom330 CPU, 76 eur Codegen MX31 case including 420W PSU, 46 eur 2Gb DDR2 memory stick, 46eur Samsung 320Gb HDD, 44eur Labtec keyaboard + mouse, 17eur … Continue reading Atom330/ITX computer for EMC2 lathe-control
Just had a 2-3 year old SATA drive fail on me. If you're reading this, go and take backups of critical data. Do it. Now. This is the cnc-mill controller machine so hopefully no critical data was lost. Some notes on the EMC2 install process, just in case I need to do it all over … Continue reading Hard disks are not forever