User Guide

14
In theory, Wi-Fi is a faster technology than the 10/100 Mb/s
Ethernet circuit that is built-in to the Pi 2 Model B. In practice,
however, this is not always the case. As the Pi cannot process
data as quickly as a brand new desktop computer, the difference
in speed between Ethernet and Wi-Fi is less noticeable and you
should use whichever is most convenient for you.
1.4 SD Cards
In the next chapter, you will learn about Raspberry Pi operating
systems (in particularly, Raspbian Linux) and how to install them
onto a secure digital (SD) card. This will complete the set-up of
the Pi.
Unlike conventional desktop computer systems, the Pi does not
have a hard drive from which to load an operating system.
Instead, it uses the card socket to load files from a memory card.
When the Pi is first turned on:
1. The main ARM processor and SDRAM (memory) are
disabled.
2. The graphics processing unit (GPU) loads the “first-
stage bootloader” that is built-in to the Pi, and this
contains all of the code necessary to work with
memory cards.
3. The first-stage bootloader enables SDRAM, detects
the presence of a memory card, and loads the
“second-stage bootloader” from it.
4. The second-stage bootloader loads the operating
system or bootable program from the card.
Not all Wi-Fi and Ethernet adaptors are compatible with the
Raspberry Pi. Before buying, check that the adaptor is known to
be working by looking at the list at
http://elinux.org/RPi_USB_Wi-Fi_Adapters