Plugwash and philE - Thank you so very much for the additional history and background. Those were definitely the missing pieces in my understanding. Have a great day!

Thanks for the help! That diagram is only a partial one. It just shows some of the peripheral circuitry of the Pi If the Pi actually had a Southbridge and Northbridge (terms that don't really apply here), they would be inside the main Broadcom chip along with the CPUs, GPU and pretty much everything...

I'm not quite sure which hardware forum to post to. If this is not the right one, please let me know. Looking at the Raspberry Pi 3 B+ schematic here: https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/rpi_SCH_3bplus_1p0_reduced.pdf I'm trying to understand what part of that d...