Fundamental PC Concepts
Fundamentally, PCs haven’t changed that much in the last
decade or two. Sure, you’re now sporting a terabyte of hard disk space and 3GB
of RAM, but the core hardware of a machine is basically the same. We are going
to dissect different components of a PC and show you how it all works together
to produce that fancy computer sitting on your desktop today. For many of you,
this will be a review of what you already know but for some of you, you will
find components and parts you are unfamiliar with. We understand if you are
adept at computer hardware and speed read these sections – don’t skip them
outright, there might be a useful exam passing tip here and there.
Storage Devices
Storage devices are hardware which is used to store files
and data. This includes floppy disk drives (FDD), hard disk drives (HDD), CD &
DVD drives (Optical drives), and all sorts of removable storage – thumb
drives, flash drives, SD cards, memory sticks, tape backup drives, USB drives.
In this section, we need to identify what each type of
storage is and what characteristics each has.
Floppy Drives
Ok, raise your hand if you have a newer computer with a
floppy drive in it? Anyone? Anyone? Ok, maybe a few of you do, but floppy
drives are a technology which has gone by the wayside. Several years back,
Dell made the decision to cut out floppy drives. The other manufacturers were
quick to follow.
There are two primary types of floppy drives that existed
in the early years of the PC industry: 3-1/2” and 5-1/4”. If you can find a PC
in your company which has a 5-1/4” floppy drive, I give you props – and a
recommendation to clean out your old PCs. 5-1/4” floppy drives have been gone
from mainstream PCs for a long time and you can rest knowing you won’t be
quizzed about them on the CompTIA A+ exam. If they do ask you a question about
one, choose E) Has not been sold in a new PC for more than 10 years.
Unfortunately, a few 3-1/2” floppy drives still exist so we
have to discuss them here. By the time A+ 2009 comes out, I imagine they will
disappear from the exam – like Windows 95 did in the 2006 update.
The images above show a 3-1/2” floppy and a 5-1/4” floppy.
The 3-1/2” floppy has a hard outside shell while the 5-1/4” floppy was, well,
floppy. In the early days of tech support, the 3-1/2” floppy was often
referred to by users as a “hard disk” – because they just didn’t know any
better.
Figure 1: 3-1/2" Floppy Drive
Note from the
Field: If you have a few floppies still lying around, keep them,
they can be very useful. I was consulting with a client the other day who had
several old Compaq ProLiant servers. Compaq ProLiants come with a nice setup
utility called SmartStart. Due to the age of this equipment, I had to use an
older version of SmartStart which required a floppy disk to setup Windows.
Guess what I couldn’t find? I ended up rummaging through some boxes in my
basement and finding an old driver disk I could reformat for the server setup.
Hard Disk Drives
Hard disk drives are often referred to as “mass storage
devices” – they can hold a large amount of data and in the context of this
section, are “fixed” – installed in a PC. Later, we will discuss external hard
disk drives. In early PCs, hard disk drives were measured in megabytes, now it’s
mostly gigabytes, though manufacturers are breaking the terabyte level on some
newer drives.
Figure 2: Hard Disk Drive
Figure 3: The Insides of a Hard Disk Drive
Hard drives come in many different physical sizes, speeds,
and connector types. The guts of a hard drive are all basically the same: it
contains one or more platters with a head which reads data. You will often hear
speed described in RPM: 5400RPM, 7200RPM, 10,000RPM, and even 15,000RPM. The
higher the number, the faster the drive spins the platter and can read data.
Typically you will only see 10,000RPM (also called 10K) and 15,000RPM (15k)
drives in servers or high-end workstations.
Speed is also measured by the data transfer speeds which is
limited by the type of connector the hard drive uses. We will discuss speeds
with each connector section.
Hot-Swappable
Most Hard Drives are fixed inside desktop PCs, but servers
frequently contain hot-swappable hard drives. A
hot-swappable drive is mounted inside a special drive cage which can be pulled
out and replaced while the server is on. You don’t want to remove a hard drive
from a desktop PC while it is still running!
Hot-swappable drives are important in servers as
uptime is extremely important. Most server
configurations use some sort of redundant drives (RAID technology) to have data
spread across multiple drives. In a RAID 5 configuration, for example, you can
have one drive fail and the data will be safe. A hot-swappable drive can be
replaced and rebuilt in the array without shutting down the server. You won’t
need to know all of this for the exam, but be familiar with the term
hot-swappable and what it means.
Hard Drive Connectors
In a couple of sections, we will discuss several different
connector types on the motherboard or add-on cards for connecting drives. In
this section, we are going to discuss those connector and cable types in detail
so you can understand them for the exam. There are basically three types of
connector types you need to be aware of for the exam: IDE (EIDE), SATA, and
SCSI.
IDE (EIDE/PATA)
For years, IDE and its successor EIDE were the most popular
drive adapter types on the market. It is still in use and is frequently used to
connect CD-ROM and DVD-ROM drives even if your system has SATA or SCSI for the
hard drives.
Figure 4: IDE Ribbon Cable
Figure 5: IDE Rounded Cable
IDE refers to the ATA technology specification. Another name
for the ATA disk drive technology is Parallel ATA, or PATA, compared with our
next drive connector type Serial ATA (SATA).
Figure 6: 4 Pin Molex Power Connector - ATA Drives
ATA has several different versions which all use the
connector and cables shown above.
ATA: Commonly referred to as
an IDE connection, ATA supports a maximum of 2 drives. It is a 16-bit interface.
ATA-2: Sold as Fast ATA or
Enhanced IDE (EIDE), ATA-2 supports block transfers and logical block
addressing.
Ultra-ATA: Supports speeds
of 33 Megabits per second.
ATA/66: Developed by Quantum
and supported by Intel, doubles ATA throughput to 66 Mbps.
ATA/100: Most frequently
used today – supports up to 100 Mbps.
SATA (Serial ATA)
Serial ATA is an evolution of the Parallel ATA connectors we
discussed above (in the form of IDE). Serial ATA cables are smaller allowing for
easier airflow in computers. Additionally, they are faster than ATA with speeds
at 150 Megabytes per second and 300 Megabytes per second (1.5 Gbits and 3.0
Gbits respectively).
Figure 7: SATA Connection Cable
With a much higher data transfer rates, you can take
advantage of faster hard drives with SATA. My workstation has a 150GB 10,000 RPM
Seagate Cheetah drive as the boot drive – very fast!
SATA also supports hot pluggable drives while Parallel ATA
does not. For this reason, SATA has replaced some of the lead SCSI has in the
server market, allowing server vendors to reduce some cost in their server
systems.
Figure 8: SATA Power Connector
Whereas the ATA drives use a 4 pin molex power connector,
most SATA drives use a new flat style power cable.
SCSI
Small Computer System Interface, or SCSI, has been around for
a long time in the computer industry. Once the only interface on Apple Macintosh
systems and still used in a variety of servers and workstations, SCSI is a very
reliable and fast connector which is frequently used in RAID configurations with
multiple hard drives for redundancy.
