9.4: SOC (System on Chip)
- Page ID
- 470291
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The SoC is the CPU (Central Processing Unit) and the GPU (Graphical Processing Unit)
Figure \(\PageIndex{1}\): SoC or Raspberry Pi 4B. (Belford cc 0.0)You should add a heat sink to your SoC. Pi 4 have Dynamic Voltage and Frequency Scaling (DVFS) which allows SoC components to run at lower voltages and reduces clock speed when not needed. The memory is split between the GPU and CPU and you can identify how much each is allocated with the following command.
vcgencmd get_mem arm && vcgencmd get_mem gpu
The Top command gives general information on system performance (CPU and memory)
top
CPU
The CPU (Central Processing Unit) is the "brain" of the computer. It "fetches", "decodes" and "executes" code with each step being performed at a rate determined by the clock. A multicore architecture allows parallel processes to occur. If you want to do a dive into how computers work you should check out the PBS Crash Course on Computer Science with Video 8 being on the CPU
Different versions of the Pi use different CPUs, which can be found on the Raspberry Pi Processors page of the Pi Documentation. the Pi 3 uses a BCM2837B0 and information can be found here.
- 64 bit Quad Core Broadcom BCM2711 (Pi 4)
- 1.8 GHz (clock speed)
- BCM2711 ARM Peripherals Documentation
- section 5.3 has alternative GPIO pin assignments
- SRM Cortex-A72 Cores
- Architecture handles "out of order" execution
- prioritizes performance over efficiency.
- one of the reasons the Pi 4 gets hotter than a pi 3
- Caches
- 32 KB data and 48 KB Instruction L1 per core, 1 MB L2 shared cache
Some CPU commands
To get Information on your CPU
cat /proc/cpuinfo
To get CPU temperature
vcgencmd measure_temp
To find the clock speed your Pi configuration is limited to
vcgencmd get_config arm_freq
to find current clock speed
cat /sys/devices/system//cpu/cpu0/cpufreq/scaling_cur_freq
GPU
- 32 bit Broadcom VideoCore 6
- 500 mHz
- supports Open GL ES 3
- Runs 4K video decoder at 60 frames/sec
- 500 mHz