Exploring Storage and Expansion Devices
Over the following sections, I will introduce you to six different types of devices. The first two, hard drives and optical drives, give you the ability to store data on a long-term basis. The last four, video cards, soundcards, network cards, and modems, provide features that take your computer from being a really good paperweight to being a helpful and fun device to use
Over the following sections, I will introduce you to six different types of devices. The first two, hard drives and optical drives, give you the ability to store data on a long-term basis. The last four, video cards, soundcards, network cards, and modems, provide features that take your computer from being a really good paperweight to being a helpful and fun device to use.
Hard Drives
Computers would be a lot
less useful to us if
they weren’t able to
store our data
long-term. This is where
hard drives come in.
Hard disk drive (HDD)
systems (called hard
disks or
hard drives
for short) are used for
permanent storage and
quick access. They hold
our data as well as
files the system needs
to operate smoothly.
Drives differ in their
capacity, their speed
(access time), and the
type of materials they
are made from (metal or
glass platters coated
with a magnetic
coating).
Hard disks typically
reside inside the
computer, where they are
semipermanently mounted
with no external access
(although there are
external and removable
hard drives), and can
hold more information
than other forms of
storage. Hard drives use
a magnetic storage
medium and are known as
conventional drives to
differentiate them from
newer solid-state
storage media.
Inside a conventional,
spinning disk hard
drive, you will find a
sealed stack of metal
platters, each with a
read-write head on a
retractable arm that
reads data from and
writes data to the
platters by magnetizing
bits of iron oxide
particles on the
platters in patterns of
positive and negative
polarity. As a hard disk
operates, the platters
rotate at a high speed,
and the read/write heads
hover just over the disk
surfaces on a cushion of
air generated by the
spinning. Normally, you
won’t see the inside of
a hard drive, so you can
see one in Figure 1.20.
Once you open the metal
box in which it’s
encased, you ruin the
drive. The platters are
typically 3½″ in
diameter for full-size
hard disk drives (for
desktop PCs) and 2½″ for
smaller hard disk drives
used in laptops.
Hard disks typically reside inside the computer, where they are semipermanently mounted with no external access (although there are external and removable hard drives), and can hold more information than other forms of storage. Hard drives use a magnetic storage medium and are known as conventional drives to differentiate them from newer solid-state storage media.
Inside a conventional, spinning disk hard drive, you will find a sealed stack of metal platters, each with a read-write head on a retractable arm that reads data from and writes data to the platters by magnetizing bits of iron oxide particles on the platters in patterns of positive and negative polarity. As a hard disk operates, the platters rotate at a high speed, and the read/write heads hover just over the disk surfaces on a cushion of air generated by the spinning. Normally, you won’t see the inside of a hard drive, so you can see one in Figure 1.20. Once you open the metal box in which it’s encased, you ruin the drive. The platters are typically 3½″ in diameter for full-size hard disk drives (for desktop PCs) and 2½″ for smaller hard disk drives used in laptops.
The two most common sizes were 3½″ and 5¼″, and they held 1.44 MB and 1.2 MB, respectively. You won’t need to know those numbers for the exam, but they give you a good perspective on how little data they could hold. The one advantage they had was that they were portable. Now we have USB flash drives, with capacities in the gigabytes (and no special read/write device required), which make floppy disks obsolete.
Hard Drive Characteristics
When evaluating hard drives, there are really two factors that determine their performance: size and speed.
Size is fairly self-evident. Hard drives with larger capacity store more data. There isn’t anything too tricky about it. You can easily find hard drives with capacities from several hundred gigabytes up to 10 terabytes. Table 1.2 has some conversions that will likely come in handy.
How Many | Equals | Example |
---|---|---|
1 bit | 1 bit | A single 0 or 1 |
8 bits | 1 byte | One text character |
1,000 bytes | 1 kilobyte (KB) | A 1,000-character plain-text file or a small icon |
1,000 kilobytes | 1 megabyte (MB) | A small photograph or one minute of music |
1,000 megabytes | 1 gigabyte (GB) | A full-length audio CD is about 800 MB; a two-hour DVD movie is about 4 GB. |
1,000 gigabytes | 1 terabyte (TB) | A large business database |
1,000 terabytes | 1 petabyte (PB) | Data from a large government institution, such as the U.S. Internal Revenue Service |
1,000 petabytes | 1 exabyte (EB) | It’s rumored that YouTube stores just over 1 EB of data, but it’s hard to confirm that claim. |
1,000 exabytes | 1 zettabyte (ZB) | In 2013, NPR and Forbes reported that the U.S. National Security Agency’s new Utah data center could store up to 5 ZB of data. But it’s the NSA, so of course there is no official confirmation of this. |
The historical convention was always that the next level up equaled 1,024 of the previous level, such that 1 MB = 1,024 KB. Now, it’s more or less accepted that we just round everything off to 1,000 to make it easier to do the math. |
Most people assume that they don’t need to think in terms of exabytes or zettabytes (not to mention yottabytes, which are 1,000 zettabytes), but with 6 TB hard drives being relatively common today, these larger measures are probably right around the corner.
Speed is the other thing you will want to look at when considering a hard drive. Hard drive access is much slower than RAM access, so hard drives can often be the bottleneck in system performance. Over the years, though, technology has evolved to improve hard drive access time. To speed up data access, manufacturers increase the speed at which the platters spin from one generation of drives to the next, with multiple speeds coexisting in the marketplace for an unpredictable period until demand dies down for one or more speeds.
The following spin rates, in revolutions per minute (rpm), have been used in the industry for the platters in conventional magnetic hard disk drives:
- 5400 rpm
- 7200 rpm
- 10,000 rpm
- 12,000 rpm
- 15,000 rpm
Connecting a Hard Drive
There are two common hard drive standards in the marketplace today: Parallel ATA (PATA), also known as Integrated Drive Electronics (IDE), and Serial ATA (SATA). PATA/IDE has been around a lot longer (IDE came out in the late 1980s), and SATA is the newer and faster technology, launched in 2003.
Regardless of the standard, hard drives need two connections to function properly: power and the data cable. The power comes from the power supply, and the data cables connect to the motherboard. Figure 1.21 shows the back of two standard 3½″ desktop hard drives. The top one is PATA/IDE, and the bottom one is SATA.
Figure 1.22 shows the ends of the data cables. Again, the top one is PATA, and the bottom one is SATA. The connectors where the data cables plug into the motherboard were shown in Figure 1.9 and Figure 1.10.
Hard drives are important, and for many years the most common hard drive standard was PATA (at the time called IDE). Most motherboards came with two connectors; today, motherboards will have one, if they support PATA at all. When CD-ROM drives came out, they too used the same 40-pin connector as hard drives. If you had only two devices, this wasn’t a problem. But what if you wanted two hard drives and a CD-ROM?
The 40-pin PATA ribbon cable has three connectors on it. One goes to the motherboard, and the other two—one in the middle of the cable and one at the other end—go to drives. If you have only one PATA drive, you use the connector at the far end of the cable, and the extra connector in the middle of the cable goes unused.
If you need to connect two devices to one cable, then you also need to tell the computer which device has priority over the other. Otherwise, they fight like spoiled children and neither one will work. To do that, you need to configure each drive as either the master (MA) or the slave (SL) on that cable. Master and slave configuration is performed via jumpers on the back of the hard drive. If you look at Figure 1.21, the jumper block is the 10-pin block between the PATA data connector and the power block. The right two pins have a jumper placed over them, configuring the drive.
Some PATA cables will assign mastery or slavery to a drive based on the connector into which it’s plugged. (That’s called Cable Select [CS], with the master at the end and the slave in the middle.) To make this work, you must set the jumpers on each of the drives to the CS setting. Fortunately, they are usually set to CS by default. The top of the hard drive might have a sticker showing you the jumper settings (the one in Figure 1.21 does), or you can check the manufacturer’s documentation.
When a newly installed PATA drive doesn’t work, it could be because the jumpers aren’t set correctly.
Solid-State Drives
Unlike conventional hard drives, a solid-state drive (SSD) has no moving parts but uses the same solid-state memory technology found in the other forms of flash memory. You can think of them as bigger versions of the flash drives that are so common.
When used as a replacement for traditional HDDs, SSDs are expected to behave in a similar fashion, mainly by retaining contents even when the system is powered off. Connecting an SSD is just like connecting a regular HDD: they have the same PATA/SATA and power connectors. Most manufacturers also make them in the same physical dimensions as traditional hard drives.
As you might expect, SSDs have several advantages over their mechanical counterparts. These include the following:
- Faster start-up and read times
- Less power consumption and heat produced
- Silent operation
- Generally more reliable because of a lack of moving parts
- Less susceptible to damage from physical shock and heat production
- Higher data density per square centimeter
- The technology to build an SSD is more expensive per byte.
- All solid-state memory is limited to a finite number of write (including erase) operations. Lack of longevity could be an issue.
Optical Drives
The CDs, DVDs, and BDs used for data storage are virtually the same as those used for permanent recorded audio and video. The way data, audio, and video information is written to consumer-recordable versions makes them virtually indistinguishable from professionally manufactured discs.
Each of these media types requires an optical drive capable of reading them. Those devices are designated with a -ROM ending, for example, CD-ROM, DVD-ROM, or BD-ROM. If the drive is capable of writing to these discs (called a burner), it will have a different ending, such as -R (recordable) or -RW (rewritable). To confuse matters further, there are two standards of DVD burners: DVD-RW and DVD+RW. Today’s DVD readers can generally handle both formats, but older devices might not be able to do so. Burnable BD drives are designated BD-R or BD-RE (for re-recordable). Figure 1.26 shows a DVD-ROM. It’s really hard to tell optical drives apart from each other, unless you see the logo that’s on it.
Each of the formats I have mentioned so far has different capacities. Table 1.3 lists the most common. Before getting to Table 1.3, though, I need to define a few more acronyms. Discs can be single sided (SS) or double-sided (DS), meaning that information is written to one or both faces of the disc. In addition, DVDs and BDs can have multiple layers on the same side, otherwise known as dual-layer (DL). The ability to create dual layers nearly doubles the capacity of one side of the disc. Boldfaced capacities in the table are the commonly accepted values for their respective formats.
Disc Format | Capacity |
---|---|
CD SS (includes recordable versions) | 650 MB, 700 MB, 800 MB, 900 MB |
DVD-R/RW SS, SL | 4.71 GB (4.7 GB) |
DVD+R/RW SS, SL | 4.70 GB (4.7 GB) |
DVD-R, DVD+R DS, SL | 9.4 GB |
DVD-R SS, DL | 8.54 GB (8.5 GB) |
DVD+R SS, DL | 8.55 GB (8.5 GB) |
DVD+R DS, DL | 17.1 GB |
BD-R/RE SS, SL | 25 GB |
BD-R/RE SS, DL | 50 GB |
BD-R/RE DS, DL | 100 GB |
SS: single-sided; DS: double-sided; SL: single-layer; DL: dual-layer |
Now you know why Blu-ray movies are so much better than those on DVD. Even the simplest BD can store nearly 50 percent more data than the most advanced DVD!
Video Cards
Sometimes, video cards can include dedicated chips to perform some of these functions, thus accelerating the speed of display. This type of chip is called a graphics processing unit (GPU). Some of the common GPUs are AMD Radeon and NVIDIA GeForce. Most video cards also have their own onboard RAM. This is a good thing, and just like the RAM on your motherboard, the more the better. Figure 1.27 shows a video card.
Most video cards sold today use the PCIe interface, but you might still see some older AGP cards out there. They both work the same way, except that AGP is very slow compared to PCIe.
Video cards can have one or more external plugins for monitors or other display devices. You can see that the card shown in Figure 1.27 has three plugins—one S-video port and two DVI ports. These will be covered in more detail in Lesson 2. Also notice that this card has a rather large fan attached to it. This is because the card has its own processor and memory and generates a lot of heat. Secondary cooling is necessary to keep this card from melting down.
Sound Cards
The most popular sound card standard in the market is the Sound Blaster, which is made by Creative Technology.
Modems
Before high-speed Internet became popular, a modem was the device people used to get on the Internet. Of course, this meant that the phone line was in use and no one could call your home phone. This was back in the days when people still had land phone lines and when mobile phones were a rare luxury. (I feel like my grandpa talking about the “olden days” when I say these things!) Modems are rarely used today.