High CPU consumption by pidp8i process

[Bobby Ess]

 apologize in advance for the lengthy post but I want to ensure I provide as much detail as possible.

The short version is that the pidp8i process is consuming ~ 152% of CPU. I'm not sure when this started but there have been no changes to the stock install for several months. I recently opened an SSH session and noticed considerable lag on keyboard input. Upon further investigation I noticed the high CPU usage by the pidp8i process.

Not being able to find anything in the logs concerning errors or other anomalies, I decided to perform a fresh install.

I have a Pi 2 Model B with a 32gb MicroSD card. Using the Pi Imager, I flashed the SD card with the current Pi image, applied all updates and rebooted. I had the unit hardwired ethernet, an HDMI cable for video out, and a USB keyboard and mouse plugged in. After reboot, the pidp8i process settled in nicely at 4.6% (see attached screenshot).

I then shut the unit down, disconnected all cables including the network cable, and relocated the unit to a cabinet I use for displaying vintage technology pieces. I attached power and switched the unit on. The pidp8i process was again at ~150%.

I have since done another fresh install, taking one step at a time to find out what the possible culprit could be. On this attempt, I had all cables attached including the network cable and after rebooting, applying all updates, I get the same result. 

Thinking perhaps there was something in the Pi updates that could be throttling the unit, I flashed the card again and did not apply the updates. Same resuilt. See second screenshot.

I don't understand why the first install 'worked' in the sense that the CPU usage was minimal. A duplicate installation process still resulted in the high CPU usage.

I have tried with and without the VNC process running and have replaced RealVNC with tightvnc, to no avail.

Any and all suggestions would be appreciated.

[timr...@gmail.com]

My PiDP-8i has been up 139 days.  It's still running fine, but it is consuming 145% cpu too.  Don't know why.  Mine is on a 3B+.  Will be interesting to see what is learned about this.

[Warren Young]

On Sat, Jun 14, 2025 at 17:39 timr...@gmail.com <timr...@gmail.com> wrote:

My PiDP-8i has been up 139 days.  It's still running fine, but it is consuming 145% cpu too.  Don't know why.  Mine is on a 3B+. 

That’s normal due to the ILS. One full core for the simulator running flat-out, ~40% of a second core for the ILS, leaving 2.6 cores for other things.

This is why you can’t do my ILS on the 2B’s single core.

Could be the 3rd gen ILS, could be misconfigured for a Pi 3. Show the banner line put out by the simulator before it starts fully.

[Peter Long]

Pi 2B - 4 processors - with ILS enabled - same ~145% - still got lots left over

pidp8i@pidp8i:~ $ top

top - 10:10:40 up 423 days, 22:47,  4 users,  load average: 1.68, 1.68, 1.72

Tasks: 152 total,   3 running, 149 sleeping,   0 stopped,   0 zombie

%Cpu(s): 29.2 us,  8.4 sy,  0.0 ni, 62.4 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st

MiB Mem :    922.0 total,    144.4 free,    139.8 used,    637.7 buff/cache

MiB Swap:    100.0 total,     12.7 free,     87.2 used.    698.8 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND

  536 pidp8i    20   0   13324    960    828 R 148.0   0.1 191085:00 pidp8i-sim

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From: pid...@googlegroups.com <pid...@googlegroups.com> on behalf of Warren Young <tange...@gmail.com>
Sent: Sunday, June 15, 2025 09:53
To: timr...@gmail.com <timr...@gmail.com>
Cc: PiDP-8 <pid...@googlegroups.com>
Subject: Re: [pidp8] Re: High CPU consumption by pidp8i process

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[Bobby Ess]

The plot thickens. After running for the better part of the day, it is now at 4.9%.