Raspberry Pi 4 and bad latency.. SOLUTIONS?

More
22 Mar 2025 13:34 #324548 by hitchhiker
Hi guys!I am on a new Project and found a mesa 7c81 an 7i92 on the flewmarket... dont know why someone sell it on a flewmarket...i start reading about the 7c81 and look to my boxes and found a raspberry pi 4 b version with 8gb ram.. oki load the image for the sd card from the linuxcnc website and bring it up.i isolate cpu 1 2 3 but latency doesnt go down.

Any tips?
in the config i disable audio blueetooth and overclock to 6v and 2000mhz..

which information i can share to get the cow frome the ice?

thanks all


 

 

 
Attachments:

Please Log in or Create an account to join the conversation.

  • tommylight
  • tommylight's Avatar
  • Away
  • Moderator
  • Moderator
More
22 Mar 2025 13:56 #324552 by tommylight
Replied by tommylight on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?
try this
latency-histogram --nobase --sbinsize 1000 --show

Please Log in or Create an account to join the conversation.

More
22 Mar 2025 13:59 #324553 by hitchhiker
Replied by hitchhiker on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?
I forget 1 thing.. i use a 64gb micro sd card from the brand kexin from amazon.

amzn.eu/d/hXGglyV

Please Log in or Create an account to join the conversation.

More
22 Mar 2025 14:25 #324554 by hitchhiker
Replied by hitchhiker on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?
same values or i am wrong??


 


thanks
Attachments:

Please Log in or Create an account to join the conversation.

  • tommylight
  • tommylight's Avatar
  • Away
  • Moderator
  • Moderator
More
22 Mar 2025 16:52 #324564 by tommylight
Replied by tommylight on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?
Much better, move on to wiring and making chips!
Keep an eye when starting LinuxCNC if it complains about latency, it shows a warning usually when enabling it or later during use.

Please Log in or Create an account to join the conversation.

More
22 Mar 2025 21:25 #324586 by rodw
Your latency is a pass, move on

Please Log in or Create an account to join the conversation.

More
23 Mar 2025 06:35 #324628 by hitchhiker
Replied by hitchhiker on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?
on ny m73 i have a jitter of 1000... so what is the reason thst you say that this latency is good???? thanks

Please Log in or Create an account to join the conversation.

More
23 Mar 2025 07:27 #324630 by rodw
Assuming you use the 7c81's FGPA for stepgen and don't sofware step, you don't need a base thread so latency requirements is much relaxed. I'd be happy with anything under 130,000 with 200,000 at a pinch

Please Log in or Create an account to join the conversation.

More
23 Mar 2025 07:47 #324633 by hitchhiker
Replied by hitchhiker on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?
or a 7i92... i payed for both cards 100 euros...

so for my information... on a normal pc like optiplex 3020m or lenovo m73 tiny.. i have latency under 2000... but i never looked this way in the histogram.

can you explain me the spike?! please

Please Log in or Create an account to join the conversation.

More
23 Mar 2025 07:52 - 23 Mar 2025 07:53 #324634 by Aciera
Replied by Aciera on topic Raspberry Pi 4 and bad latency.. SOLUTIONS?

same values or i am wrong??


Note the missing spikes (colored in blue/red) at the extreme left and right of the graph.
Last edit: 23 Mar 2025 07:53 by Aciera.

Please Log in or Create an account to join the conversation.

Time to create page: 0.155 seconds
Powered by Kunena Forum