RE: Raspberry pi 5 4GB is faster than the 8GB
First, disable overclocking
to make sure you do not permanently damage your hardware.
TLDR: From a terminal shell run the following commands
root@zynthianv5://zynthian# sudo rpi-update
root@zynthianv5://zynthian# sudo rpi-eeprom-config -e
Add one of these lines to your eeprom config:
adding this line for pi5:
SDRAM_BANKLOW=1or this line for pi4:
SDRAM_BANKLOW=3
Finally reboot for the settings to apply
root@zynthianv5://zynthian# sudo reboot
Results:
I did some investigation before and after using the stream omp memory speed test.
root@zynthianv5://zynthian# wget https://www.cs.virginia.edu/stream/FTP/Code/stream.c
root@zynthianv5://zynthian# gcc -O -fopenmp stream.c -o stream_omp
Before the eeprom config:
root@zynthianv5://zynthian# ./stream_omp
-------------------------------------------------------------
STREAM version $Revision: 5.10 $
-------------------------------------------------------------
Function Best Rate MB/s Avg time Min time Max time
Copy: 5384.3 0.031705 0.029716 0.033737
Scale: 6341.1 0.026889 0.025232 0.028271
Add: 5433.2 0.045661 0.044173 0.049767
Triad: 6354.2 0.039838 0.037770 0.041719
-------------------------------------------------------------
Solution Validates: avg error less than 1.000000e-13 on all three arrays
-------------------------------------------------------------
After the rpi update, eeprom reconfig, and a full reboot…
root@zynthianv5://zynthian# ./stream_omp
-------------------------------------------------------------
STREAM version $Revision: 5.10 $
-------------------------------------------------------------
Function Best Rate MB/s Avg time Min time Max time
Copy: 7791.6 0.021560 0.020535 0.022463
Scale: 7777.6 0.021250 0.020572 0.022263
Add: 7365.6 0.034241 0.032584 0.036675
Triad: 7917.9 0.033591 0.030311 0.036343
-------------------------------------------------------------
Solution Validates: avg error less than 1.000000e-13 on all three arrays
-------------------------------------------------------------