I recently got a Flirc case for my Raspberry Pi4 and was unsure if it would help the temperature of the CPU under a heavy load. So after reading mixed impressions of similar cases with builtin heatsinks on the internet, I decided I needed to run my own tests.
TLDR; It's a good looking case that keeps the temperature low enough and Wifi still works well.
You can see in the chart that in the first test the Pi without a case is warmer at idle and hits the throttling above 83º but in the second test after installing the Pi in the case the idle temperature is lower and the peak is about 60º. And yes, it took about 7 minutes to install it in the case and reboot.
Clearly the case kept the Pi cooler which was great! The case has a solid metal top that acts as a heatsink with a black plastic cover on the top and bottom. I also wondered if the plastic cover on the top reduced the heat dissipation, so I ran the test again and found that it made no noticeable difference. So I'm keeping the plastic on top.
Here is the test setup using Graphite/Grafana on my Pi to chart the temperature.
1. add a cron script to write the Pi temp to Graphite every minute.
#!/bin/sh
# Track the PI core temp in graphite
# whisper files are in /var/lib/graphite/whisper/
CARBON_PORT=2003
CARBON_SERVER=localhost
CARBON_PREFIX=pi
DATE=`date +%s`
VALUE=`/opt/vc/bin/vcgencmd measure_temp | egrep -o '[0-9]*\.[0-9]*'`
echo "$CARBON_PREFIX.temp $VALUE $DATE" | nc -N ${CARBON_SERVER} ${CARBON_PORT}
exit $?
2. install the load tester that will warm up all 4 of the CPU cores
sudo apt install stress-ng
3. the 10 minute stress test command
sudo stress-ng --cpu 0 --cpu-method fft -t 600 --times --tz --perf
The results without a case had fewer CPU cycles due to the throttling.
stress-ng: info: [26124] dispatching hogs: 4 cpu
stress-ng: info: [26124] cache allocate: using defaults, can't determine cache details from sysfs
stress-ng: info: [26124] successful run completed in 600.88s (10 mins, 0.88 secs)
stress-ng: info: [26124] cpu:
stress-ng: info: [26124] 3,351,213,272,324 CPU Cycles 5.58 B/sec
stress-ng: info: [26124] 5,257,128,421,496 Instructions 8.75 B/sec (1.569 instr. per cycle)
stress-ng: info: [26124] 2,355,284,116 Branch Misses 3.92 M/sec ( 0.00%)
stress-ng: info: [26124] 1,117,147,979,068 Bus Cycles 1.86 B/sec
stress-ng: info: [26124] 1,925,684,309,644 Cache References 3.20 B/sec
stress-ng: info: [26124] 70,192,888,528 Cache Misses 0.12 B/sec ( 3.65%)
stress-ng: info: [26124] 1,925,714,318,612 Cache L1D Read 3.20 B/sec
stress-ng: info: [26124] 70,209,791,620 Cache L1D Read Miss 0.12 B/sec
stress-ng: info: [26124] 601,769,965,280 Cache L1D Write 1.00 B/sec
stress-ng: info: [26124] 39,275,045,820 Cache L1D Write Miss 65.36 M/sec
stress-ng: info: [26124] 1,623,493,004,028 Cache L1I Read 2.70 B/sec
stress-ng: info: [26124] 237,104,488 Cache L1I Read Miss 0.39 M/sec
stress-ng: info: [26124] 11,372,158,076 Cache DTLB Read Miss 18.93 M/sec
stress-ng: info: [26124] 6,457,277,064 Cache DTLB Write Miss 10.75 M/sec
stress-ng: info: [26124] 3,019,056 Cache ITLB Read Miss 5.02 K/sec
stress-ng: info: [26124] 680,066,666,288 Cache BPU Read 1.13 B/sec
stress-ng: info: [26124] 2,355,275,308 Cache BPU Read Miss 3.92 M/sec
stress-ng: info: [26124] 1,316,252,132 Cache NODE Read 2.19 M/sec
stress-ng: info: [26124] 629,580,520 Cache NODE Write 1.05 M/sec
stress-ng: info: [26124] 2,311,855,064,928 CPU Clock 3.85 B/sec
stress-ng: info: [26124] 2,311,958,359,704 Task Clock 3.85 B/sec
stress-ng: info: [26124] 156 Page Faults Total 0.26 /sec
stress-ng: info: [26124] 156 Page Faults Minor 0.26 /sec
stress-ng: info: [26124] 0 Page Faults Major 0.00 /sec
stress-ng: info: [26124] 130,392 Context Switches 217.00 /sec
stress-ng: info: [26124] 916 CPU Migrations 1.52 /sec
stress-ng: info: [26124] 0 Alignment Faults 0.00 /sec
stress-ng: info: [26124] 0 Emulation Faults 0.00 /sec
stress-ng: info: [26124] 376 System Call Enter 0.63 /sec
stress-ng: info: [26124] 372 System Call Exit 0.62 /sec
stress-ng: info: [26124] 1,288 Kmalloc 2.14 /sec
stress-ng: info: [26124] 0 Kmalloc Node 0.00 /sec
stress-ng: info: [26124] 4,920 Kfree 8.19 /sec
stress-ng: info: [26124] 7,924 Kmem Cache Alloc 13.19 /sec
stress-ng: info: [26124] 0 Kmem Cache Alloc Node 0.00 /sec
stress-ng: info: [26124] 21,684 Kmem Cache Free 36.09 /sec
stress-ng: info: [26124] 496 MM Page Alloc 0.83 /sec
stress-ng: info: [26124] 2,496 MM Page Free 4.15 /sec
stress-ng: info: [26124] 1,481,552 RCU Utilization 2.47 K/sec
stress-ng: info: [26124] 732 Sched Migrate Task 1.22 /sec
stress-ng: info: [26124] 0 Sched Move NUMA 0.00 /sec
stress-ng: info: [26124] 127,900 Sched Wakeup 212.86 /sec
stress-ng: info: [26124] 0 Sched Proc Exec 0.00 /sec
stress-ng: info: [26124] 0 Sched Proc Exit 0.00 /sec
stress-ng: info: [26124] 0 Sched Proc Fork 0.00 /sec
stress-ng: info: [26124] 136 Sched Proc Free 0.23 /sec
stress-ng: info: [26124] 0 Sched Proc Hang 0.00 /sec
stress-ng: info: [26124] 0 Sched Proc Wait 0.00 /sec
stress-ng: info: [26124] 130,392 Sched Switch 217.00 /sec
stress-ng: info: [26124] 4 Signal Generate 0.01 /sec
stress-ng: info: [26124] 4 Signal Deliver 0.01 /sec
stress-ng: info: [26124] 710,424 IRQ Entry 1.18 K/sec
stress-ng: info: [26124] 710,424 IRQ Exit 1.18 K/sec
stress-ng: info: [26124] 84,488 Soft IRQ Entry 140.61 /sec
stress-ng: info: [26124] 84,488 Soft IRQ Exit 140.61 /sec
stress-ng: info: [26124] 0 Writeback Dirty Inode 0.00 /sec
stress-ng: info: [26124] 0 Writeback Dirty Page 0.00 /sec
stress-ng: info: [26124] 0 Migrate MM Pages 0.00 /sec
stress-ng: info: [26124] 3,304 SKB Consume 5.50 /sec
stress-ng: info: [26124] 1,016 SKB Kfree 1.69 /sec
stress-ng: info: [26124] cpu:
stress-ng: info: [26124] cpu-thermal 82.05 °C
stress-ng: info: [26124] for a 600.88s run time:
stress-ng: info: [26124] 2403.51s available CPU time
stress-ng: info: [26124] 2310.76s user time ( 96.14%)
stress-ng: info: [26124] 4.64s system time ( 0.19%)
stress-ng: info: [26124] 2315.40s total time ( 96.33%)
stress-ng: info: [26124] load average: 4.24 3.60 2.36
The results with the case
stress-ng: info: [2458] dispatching hogs: 4 cpu
stress-ng: info: [2458] cache allocate: using defaults, can't determine cache details from sysfs
stress-ng: info: [2458] successful run completed in 600.89s (10 mins, 0.89 secs)
stress-ng: info: [2458] cpu:
stress-ng: info: [2458] 3,466,468,096,172 CPU Cycles 5.77 B/sec
stress-ng: info: [2458] 5,433,442,835,240 Instructions 9.04 B/sec (1.567 instr. per cycle)
stress-ng: info: [2458] 2,428,481,032 Branch Misses 4.04 M/sec ( 0.00%)
stress-ng: info: [2458] 1,155,591,178,712 Bus Cycles 1.92 B/sec
stress-ng: info: [2458] 1,990,529,210,212 Cache References 3.31 B/sec
stress-ng: info: [2458] 72,971,962,212 Cache Misses 0.12 B/sec ( 3.67%)
stress-ng: info: [2458] 1,990,582,334,864 Cache L1D Read 3.31 B/sec
stress-ng: info: [2458] 72,956,292,228 Cache L1D Read Miss 0.12 B/sec
stress-ng: info: [2458] 621,927,779,860 Cache L1D Write 1.04 B/sec
stress-ng: info: [2458] 40,460,573,360 Cache L1D Write Miss 67.33 M/sec
stress-ng: info: [2458] 1,667,242,631,912 Cache L1I Read 2.77 B/sec
stress-ng: info: [2458] 232,913,956 Cache L1I Read Miss 0.39 M/sec
stress-ng: info: [2458] 11,851,802,864 Cache DTLB Read Miss 19.72 M/sec
stress-ng: info: [2458] 6,597,373,720 Cache DTLB Write Miss 10.98 M/sec
stress-ng: info: [2458] 3,412,088 Cache ITLB Read Miss 5.68 K/sec
stress-ng: info: [2458] 702,798,169,272 Cache BPU Read 1.17 B/sec
stress-ng: info: [2458] 2,428,041,468 Cache BPU Read Miss 4.04 M/sec
stress-ng: info: [2458] 866,617,940 Cache NODE Read 1.44 M/sec
stress-ng: info: [2458] 331,821,000 Cache NODE Write 0.55 M/sec
stress-ng: info: [2458] 2,321,089,381,860 CPU Clock 3.86 B/sec
stress-ng: info: [2458] 2,321,181,986,648 Task Clock 3.86 B/sec
stress-ng: info: [2458] 156 Page Faults Total 0.26 /sec
stress-ng: info: [2458] 156 Page Faults Minor 0.26 /sec
stress-ng: info: [2458] 0 Page Faults Major 0.00 /sec
stress-ng: info: [2458] 108,616 Context Switches 180.76 /sec
stress-ng: info: [2458] 776 CPU Migrations 1.29 /sec
stress-ng: info: [2458] 0 Alignment Faults 0.00 /sec
stress-ng: info: [2458] 0 Emulation Faults 0.00 /sec
stress-ng: info: [2458] 376 System Call Enter 0.63 /sec
stress-ng: info: [2458] 372 System Call Exit 0.62 /sec
stress-ng: info: [2458] 1,476 Kmalloc 2.46 /sec
stress-ng: info: [2458] 0 Kmalloc Node 0.00 /sec
stress-ng: info: [2458] 7,296 Kfree 12.14 /sec
stress-ng: info: [2458] 13,092 Kmem Cache Alloc 21.79 /sec
stress-ng: info: [2458] 0 Kmem Cache Alloc Node 0.00 /sec
stress-ng: info: [2458] 27,704 Kmem Cache Free 46.10 /sec
stress-ng: info: [2458] 648 MM Page Alloc 1.08 /sec
stress-ng: info: [2458] 4,620 MM Page Free 7.69 /sec
stress-ng: info: [2458] 1,485,888 RCU Utilization 2.47 K/sec
stress-ng: info: [2458] 1,348 Sched Migrate Task 2.24 /sec
stress-ng: info: [2458] 0 Sched Move NUMA 0.00 /sec
stress-ng: info: [2458] 107,156 Sched Wakeup 178.33 /sec
stress-ng: info: [2458] 0 Sched Proc Exec 0.00 /sec
stress-ng: info: [2458] 0 Sched Proc Exit 0.00 /sec
stress-ng: info: [2458] 0 Sched Proc Fork 0.00 /sec
stress-ng: info: [2458] 228 Sched Proc Free 0.38 /sec
stress-ng: info: [2458] 0 Sched Proc Hang 0.00 /sec
stress-ng: info: [2458] 0 Sched Proc Wait 0.00 /sec
stress-ng: info: [2458] 108,616 Sched Switch 180.76 /sec
stress-ng: info: [2458] 0 Signal Generate 0.00 /sec
stress-ng: info: [2458] 4 Signal Deliver 0.01 /sec
stress-ng: info: [2458] 702,072 IRQ Entry 1.17 K/sec
stress-ng: info: [2458] 702,072 IRQ Exit 1.17 K/sec
stress-ng: info: [2458] 115,840 Soft IRQ Entry 192.78 /sec
stress-ng: info: [2458] 115,840 Soft IRQ Exit 192.78 /sec
stress-ng: info: [2458] 0 Writeback Dirty Inode 0.00 /sec
stress-ng: info: [2458] 0 Writeback Dirty Page 0.00 /sec
stress-ng: info: [2458] 0 Migrate MM Pages 0.00 /sec
stress-ng: info: [2458] 3,436 SKB Consume 5.72 /sec
stress-ng: info: [2458] 1,148 SKB Kfree 1.91 /sec
stress-ng: info: [2458] cpu:
stress-ng: info: [2458] cpu-thermal 59.77 °C
stress-ng: info: [2458] for a 600.89s run time:
stress-ng: info: [2458] 2403.56s available CPU time
stress-ng: info: [2458] 2315.14s user time ( 96.32%)
stress-ng: info: [2458] 3.44s system time ( 0.14%)
stress-ng: info: [2458] 2318.58s total time ( 96.46%)
stress-ng: info: [2458] load average: 4.00 3.59 2.04
That's it.
