This page details the processor's "glue logic":
Unlike older models where the WiFi chip was mounted on an SD card-sized adapter, the Pi 4 has a surface-mount module (usually Cypress or Murata) directly on the PCB. The schematic shows how this connects via SDIO for WiFi and UART/PCM for Bluetooth. Raspberry Pi 4 Model B Full Schematic
If you are building an IoT device and having signal issues, checking the antenna trace and the ground planes (referenced in the schematic) can be enlightening. This page details the processor's "glue logic": Unlike
The Pi 4 uses LPDDR4 SDRAM, which is significantly faster than the SDRAM on the Pi 3. On the schematic, you can see the address and data buses connecting the processor to the RAM chip. The Pi 4 uses LPDDR4 SDRAM, which is
What makes this interesting is the sheer density of connections. High-speed memory routing requires precise impedance matching and length tuning—something you can't see on the schematic, but the number of lines gives you an appreciation for the engineering required to prevent signal integrity issues.