Hardware Reference
In-Depth Information
The Model B has two USB ports on the right-hand edge of the board, providing connectivity
for a keyboard and mouse, and still leaving two spare ports for additional accessories such as
external storage devices or hardware interfaces. Additionally, it includes an
Ethernet
port for
connecting the Pi to a wired network; this allows the Pi to access the Internet, and allows
other devices on the network to access the Pi—providing, that is, they know the username
and password or the Pi has been set up as a server as described in Chapter 10, “The Pi as a
Web Server”.
A History of Model B PCB Revisions
Although the Raspberry Pi Model B currently has 512MB of memory and two USB ports, this
wasn't always the case. The Model B available today is known as
Revision 2
, as it is the second
board to be made with the Model B designation. If you have bought a Raspberry Pi Model B
second-hand, or purchased it some time ago, you may have a Revision 1 board, which has a
few differences.
Revision 1
The original Raspberry Pi Model B, the Revision 1 board has just 256MB of RAM. It also has
a slightly different GPIO header, which looks identical to those of later revisions but has
certain features assigned to different pins, as explained in Chapter 14, “The GPIO Port”. This
is the most important difference: all other Raspberry Pi revisions and models share the same
GPIO layout, so if you have an original Model B Revision 1 you may need to adjust instruc-
tions and programs before they can be used successfully.
Revision 2
Introduced shortly before the launch of the Model A, the Raspberry Pi Revision 2 includes
double the memory of the original at 512MB. It also introduces the new, standardised GPIO
header shared with the Model A. An extra header, which is also present on Model A boards,
marked P5 and located just below the GPIO header, is a sure sign that a Model B is the newer
Revision 2.
A Bit of Background
Before heading into Chapter 2, “Getting Started with the Raspberry Pi”, it's a good idea to famil-
iarise yourself with some background details of the Pi and its creation. While the Pi is usable as
a general-purpose computer, capable of performing the same tasks as any desktop, laptop or
server—albeit more slowly—it is designed as a
single-board computer
aimed at hobbyists and
educational use, and as such differs from a “normal” computer in a couple of important ways.
