| An Overview Of SCSI | | Print | |
a standard type of input and output system used to attach peripheral devices to
provide a very fast connection rate. These devices can be scanners, hard disks or
other devices that can connect to a computer. Most Mac computers and operating
systems use SCSI connections and they come in a several varieties.
The purpose of using SCSI connections is that the transfer rate is much faster than
parallel ports. Data can be transferred up to 160 megabytes per second than
standard serial and parallel ports. Also, many devices can be attached to a SCSI
port.
The SCSI ports are most commonly used for peripheral devices such as hard disks,
tape storage devices and printers. CD ROM drives, CD burners and recorders and
DVD drives are also able to connect to SCSI ports. Even SCSI compatible printers
can be purchased and compatible with the SCSI system. Most devices that are
compatible with SCSI will have a built in terminator that can either be enabled or
disabled. If the device does not have an active terminator already built in, one can
be purchased. There are several varieties of SCSI cables available because the SCSI
system is so flexible.
There are many benefits to using SCSI. SCSI provides a high-speed, intelligent
interacing that can allow for up to 16 different peripheral connections on a single
bus.. The faster the SCSI transer rate, the faster the data and information is
available to the user. The SCSI is also very reliable and it works on most computer
systems. The problems with SCSI are few. One potential problem is when using
SCIS, it must be configured for a specific computer. The SCSI also has limited BIOS
support and there is no common software inferface. Another potential problem while
using SCSI is that it has many variations that can be confusing to a new user.
There are three basic types of SCSI. The SCSI-1 was the first type of SCSI that was
developed in 1986. The SCSI-2 was the second variation that was became a
standard in 1994. The key component to SCSI-2 was the inclusion of the CCS
(Common Command Set). These are the 18 commands considered to be necessary
to make any SCSI device run smoothly. Also included in the SCSI-2 is the command
queing which allowed that any SCSI device to store a series of commands from the
host computer.
This queing determines which commands are given first priority.
The third variation of SCSI is the SCSI-3, which came soon after the second variation
in 1995. This variation can sometimes be confusing to the new user. This variation is
not considered the standard since it has smaller built-in standards than the SCSI-2.
The SCSI-3 uses other variations including Ultra, Ultra2, and Ultra3. The fast and
wide designations work like the SCSI-2 and the fast designation means that the
speed has been doubled. The SCSI-3 can add functionality and performance
improvements to the system in use. The SCSI-3 also uses glass fiber optic cables
instead of traditional ribbon cable connections.
There are three main parts of any SCSI system. These include the controller or host
adapter, the device and the cable. The controller is the main part of the SCSI
system. It serves as an interface between any devices connected to the unit. The
controller might be a built into the motherboard device or it might be a card that can
be plugged in to the computer. The controller also contains the BIOS, which is the
ROM or software memory chip that controls devices hooked into the SCSI. Most
devices that are connected with the SCSI have a built in adapter that allows the unit
to communicate. These devices are called embedded SCSI devices.
Another thing to remember when looking at SCSI is that SCSI is not the same as
SASI, which was developed in the 70s. SASI was originally designed to work with
disk drives only. SASI also operated much slower at 1.5 MB second than the newer
SCSI. The older version of SCSI-1 was based on the SASI system making the SASI
system obsolete. The two systems cannot be used together.
An Overview Of WiFi
WiFi is short for “wireless fidelity” and is a wireless local area network that uses high
frequency radio signals to transmit and receive data over distances of a few hundred
feet. The WiFi route uses an Ethernet protocol, which is different than using a wired
Internet system. The WiFi system is a good alternative to wired LAN systems. Many
buildings, airports, hotels and public places now offer WiFi networks so people can
have portable access to the Internet.
These locations are often called hotspots. WiFi, also called 802.11 networking or
wireless networking, is a good way to handle wireless network. The biggest
advantage of using WiFi is it is a simple and portable way to connect to the Internet.
Several computers in one location can be connected together without using cables or
wires. This is a big advantage to businesses that need several computers to access
the web. Computers that connect using a WiFi system will connect to the network
utilizing radio tower signals.
Computers can still connect to each other via WiFi and still be up to 100 feet apart.
There are some disadvantages of using a WiFi connection. Just as in any radio
transmission, a wireless network has the potential for radio interference. This maybe
caused by bad weather or interference from other wireless devices. Obstructions,
such as walls or buildings, can also cause interference with a WiFi connection.
Many users though, feel that the advantages far outweigh the disadvantages.
WiFi connections that work with 802.11b and 802.11g transmissions can transmit
waves at 2.4 GHz. The higher frequency allows the higher data rate. A WiFi
connection can transmit data up to 100 times faster than a traditional dial-up
connection. In addition, a WiFi connection can change frequencies when necessary.
The connection is designed to hop the radio bandwidth and is resistant to
interference.
Connecting a computer to WiFi is relatively simple. Most new laptops come equipped
with a WiFi card built in. Older laptops can also be compatible with WiFi with an
added card. To add a WiFi card to a laptop, purchase a PCMCIA card or buy an
external adapter and plug it in the USB port. The card and driver are then installed
on the computer. After installing, it is necessary to find a hotspot to access the
Internet and email services. Most new computers will automatically connect to the
hotspot and a connection will be established.
A hotspot will be the connection point for WiFi access. It is a small box that is
hardwired into the Internet. It transmits radio waves that are compatible with the
WiFi network. Many public places have WiFi hotspots. These can often be found in
restaurants, hotels, libraries and airports.
Hotspots can also be created at home. These hotspots in the home can be
established by purchasing a Wireless Access Point Router. The Wireless Access Point
Router is a box that contains a connection port, a router, an Ethernet hub, a firewall
and a wireless access point. Once this is turned on, the hotspot will have coverage of
around 100 feet in all directions. Most homes can get adequate coverage throughout
the house. Signal boosters can also be purchased to increase the hotspot range.
When looking to purchase a WiFi system for the home, the 802.11b is usually less
expensive, but it of the lowest quality.
The 802.11g cost more, but is fast and works better in most homes.
It is important to remember that WiFi connections can either be open or secure.
When a hotspot is open and security is an issue such as when using the network on a
regular basis at home, it is necessary to use a WEP or Wired Equivalent Privacy, key
to connect. This is a type of encryption system. When using a WEP key, the user will
need to enter the code before gaining access to the WiFi network. Using a WEP key
ensures that all of the data is protected at the same level as wired networks.
If the computer in use has access to a broadband or dial-up connection there is no
additional cost for WiFi access, but does need an attached access point. This is a low
cost device used to provide wireless access to media adaptors and laptop computers.
Access point devices can cost anywhere from $20 to $300.
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