BIOS tuning HP 8300

 Hello everyone

I'm in the process of converting my CNC router from Mach3 to LinuxCNC. I had some trouble finding the right computer, but thanks to this forum I bought a HP 8300 and got 24801ns on the base thread with 6 glxgears and video playing.

Now my question is, should I just be happy with the max jitter value, or should I try to tune my bios to get a better value? I’m using a Mesa 7i96S card. Here is my computer specs:


Product Name: HP Compaq Elite 8300 SFF
SKU Number: QV996AV
Processor Type: Intel(R) Core(™) i5-3470 
Processor Stepping: 000306A9 00000012
Cache Size (L1/L2/L3): 64KBx4 / 256KBx4 / 6144KBx1
Memory Size: 8192 MB DDR3 / 1600 MHz
     Channel A: DIMM1 4096 MB / DIMM2 0000 MB
     Channel B: DIMM3 4096 MB / DIMM4 0000 MB
System BIOS: K01 v02.90
ME Firmware Version: Disabled
Me Management Mode: Disabled

Thanks
Jens

No need for a base thread for a 7i96, all that is required is a servo thread.

The EliteDesk 800 G2 is also quite good but only the 65W model (I5-6500)
The 35W mode (I5-6500T) has latency issues.

Thanks everyone for the quick responses, this is really a great forum:) https://lh7-us.googleusercontent.com/ZikaoEIeHsCi2azZR_xuV53q7PsW2h_K1BrG_MKjyMTjg6Ck9w7_7-uA0PjimGMzjgwy8CBUMdsZGcyF24un2KX6lZz9FS2B4T8mvaOQLjHKIP-QIwb826Ew70EZteP60OoGM-jo9UTGHxQMkvS-cxYAfter your comment I did some more reading on the forum about FPGA. Do I understand this about right?:  

• LinuxCNC sends a signal through the servo thread to the FPGA. 
• This signal tells the FPGA how fast to do pulses, and the FPGA then sends out the pulses at a very regular rate.

 I couldn’t find anything about this in the documentation. What are good/decent servo thread jitter numbers when using FPGA cards? Maybe the computers I declined were good enough after all…Thanks EveryoneJensDenmark

At least for Mesa Ethernet cards what is important is that
the communication latency is not so long that packets are timed
out. The default time-out value is 80% of a servo thread interval.
A a general rule, it would be best if communication delays were less
than 50% of the servo thread period (or 500 usec)

Note that the latency test does not test communication latency
but just scheduling latency (which does add to communication latency).

You can do a rough test of Ethernet communication latency with:

ping -c 4 [FPGACard_IP_Addr]
sudo chrt 99 ping -i .001 [FPGACard_IP_Addr]

(run for several minutes and hit control C for results)

A bit fancier test with LinuxCNC running is to do a histogram:

hal-histogram  --binsize 30000 hm2_CARD.0.read.time

Note that the times in the histogram are CPU cycles on X86 hardwae


 

Thanks a lt for your reply PCW! I will try that:)

Hello!

It's great to hear about your progress in converting your CNC router from Mach3 to LinuxCNC. Achieving a max jitter of 24801ns with your HP 8300 while running multiple tasks is a decent performance, especially considering the complexity of real-time operations in CNC systems.

Regarding your question about whether to be satisfied with the current max jitter value or to attempt BIOS tuning for better performance, it's a balance between the effort involved and the potential gains. Here are a few points to consider:

Current Performance vs. Requirements: If your current jitter value meets the requirements for the precision and complexity of the work you plan to do with your CNC router, further tuning might not be necessary. LinuxCNC is quite efficient, and your current setup might be sufficient for most tasks.

Potential for Improvement: BIOS tuning can potentially improve performance, but the extent of improvement varies. Since you're using a Mesa 7i96S card, which is well-regarded in the LinuxCNC community, ensuring that your system is optimized to work seamlessly with it could be beneficial.

Risk vs. Reward: Tweaking BIOS settings comes with some risk. Incorrect settings can lead to system instability. Always make sure to document your current settings before making changes, so you can revert if needed.

Community Insights: Since you've already found this forum helpful, consider asking for specific advice about BIOS tuning for your HP 8300 in the context of LinuxCNC. Other users with similar setups might have valuable insights.

Performance Testing: If you decide to proceed with BIOS tuning, monitor the performance changes carefully. Use LinuxCNC's tools to measure any improvements in jitter and assess whether the changes positively impact your CNC router's operations.

In summary, while there's potential for improvement, it's important to weigh the effort and risk against the actual needs of your CNC operations. Your current setup seems quite capable

Too polite for a bloke & way way too generic.



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