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What is Intel's Hyper
Threading?
Intel's
Hyper-Threading technology has finally made it to market,
courtesy of the latest Xeon processors. Hyper-Threading is a
clever way of making a single chip operate like two separate
devices without implementing two cores on one die. That,
claims Intel, makes for higher performance without having to
resort to significantly larger chips or even adding a second
processor to the system.
So how does it work? HT is Intel's implementation of a
technique known as Simultaneous Multi-Threading (SMT), a
technology originally mooted for the cancelled EV8 Alpha
processor. It's also going to be implanted in IBM's Power5
processor, due 2004. Programmers have long known that some
applications will run more efficiently if they're coded into a
series parallel tasks, called threads. Modern multi-processing
operating systems can then schedule those threads to operate
on each of a system's two or more CPUs, just as it schedules
the applications and other processes themselves.
Intel's technology essentially fools the operating system into
thinking it's hooked up to two processors, allowing two
threads to be run in parallel, both on separate 'logical'
processors within the same physical processor. The OS sees
double through a mix of shared, replicated and partitioned
chip resources, such as registers, math's units and cache
memory.
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What is a Subnet?
A subnet (short
for "sub network") is an identifiably separate part of an
organization's network. Typically, a subnet may represent all
the machines at one geographic location, in one building, or
on the same local area network (LAN). Having an organization's
network divided into subnets allows it to be connected to the
Internet with a single shared network address.
Once a packet has arrived at an organization's gateway or
connection point with its unique network number, it can be
routed within the organization's internal gateways using the
subnet number as well. The router knows which bits to look at
(and which not to look at) by looking at a subnet mask. A mask
is simply a screen of numbers that tells you which numbers to
look at underneath. In a binary mask, a "1" over a number says
"Look at the number underneath"; a "0" says "Don't look."
Using a mask saves the router having to handle the entire 32
bit address; it can simply look at the bits selected by the
mask.
Using the previous example (which is a very typical case), the
combined network number and subnet number occupy 24 bits or
three of the quads. The appropriate subnet mask carried along
with the packet would be:
255.255.255.0
Or a string of all 1's for the first three quads (telling the
router to look at these) and 0's for the host number (which
the router doesn't need to look at). Subnet masking allows
routers to move the packets on more quickly.
If you have the job of creating subnets for an organization
(an activity called subletting) and specifying subnet masks,
your job may be simple or complicated depending on the size
and complexity of your organization and other factors.
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What is DirectX?
Your video card has a limited set of features. Those
features are DX8.1 compliant, meaning the card has hardware
support for all of the features contained in DX8.1.
Now, you can install DX9 on your system, but it doesn't make
your video card develop new hardware features that it didn't
have before. So, any new features introduced in DX9 that were
not included in DX8.1 will simply not be used by your card.
These features will be ignored, and only DX8.1 features will
be used.
DirectX is backwards compatible, so even if your card doesn't
have all of the features of the latest version of DX, it will
still work with it. Unsupported or missing hardware features
will simply be ignored, or in a few cases, may revert to an
earlier method which is supported by your card.
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What's an IP address?
So what is an
IP? Every machine on the Internet has a unique identifying
number, called an IP Address. A typical IP address looks like
this:
216.27.61.137
To make it easier for us humans to remember, IP addresses are
normally expressed in decimal format as a "dotted decimal
number" like the one above. But computers communicate in
binary form. Look at the same IP
address in binary:
11011000.00011011.00111101.10001001
The four numbers in an IP address are called octets, because
they each have eight positions when viewed in binary form. If
you add all the positions together, you get 32, which is why
IP addresses are considered 32-bit numbers. Since each of the
eight positions can have two different states (1 or 0) the
total number of possible combinations per octet is 28 or 256.
So each octet can contain any value between 0 and 255. Combine
the four octets and you get 232 or a possible 4,294,967,296
unique values! Out of the almost 4.3 billion possible
combinations, certain values are restricted from use as
typical IP addresses. For example, the IP address 0.0.0.0 is
reserved for the default network and the address
255.255.255.255 is used for broadcasts. The octets serve a
purpose other than simply separating the numbers. They are
used to create classes of IP addresses that can be assigned to
a particular business, government or other entity based on
size and need. The octets are split into two sections: Net and
Host. The Net section always contains the first octet. It is
used to identify the network that a computer belongs to. Host
(sometimes referred to as Node) identifies the actual computer
on the network. The Host section always contains the last
octet. There are five IP classes plus certain special
addresses: What types of IP's are there? There are two types,
public and internal. Public IP's are assigned to you by your
ISP or Network Administrator that gets them from your
provider. There are 5 classes of Public IP's:
Class A -
This class is for very large networks, such as a
major international company might have. IP addresses with a
first octet from 1 to 126 are part of this class. The other
three octets are used to identify each host. This means that
there are 126 Class A networks each with 16,777,214 possible
hosts for a total of 2,147,483,648 unique IP addresses. Class
A networks account for half of the total available IP
addresses. In Class A networks, the high order bit value (the
very first binary number) in the first octet is always 0.
Class B -
Class B is used for medium-sized networks. A good
example is a large college campus. IP addresses with a first
octet from 128 to 191 are part of this class. Class B
addresses also include the second octet as part of the Net
identifier. The other two octets are used to identify each
host. This means that there are 16,384. Class B networks each
with 65,534 possible hosts for a total of 1,073,741,824 unique
IP addresses. Class B networks make up a quarter of the total
available IP addresses. Class B networks have a first bit
value of 1 and a second bit value of 0 in the first octet.
Class C -
Class C addresses are commonly used for small to
mid-size businesses. IP addresses with a first octet from 192
to 223 are part of this class. Class C addresses also include
the second and third octets as part of the Net identifier. The
last octet is used to identify each host. This means that
there are 2,097,152 Class C networks each with 254 possible
hosts for a total of 536,870,912 unique IP addresses. Class C
networks make up an eighth of the total available IP
addresses. Class C networks have a first bit value of 1,
second bit value of 1 and a third bit value of 0 in the first
octet.
Class D -
Used for multicasts, Class D is slightly different
from the first three classes. It has a first bit value of 1,
second bit value of 1, third bit value of 1 and fourth bit
value of 0. The other 28 bits are used to identify the group
of computers the multicast message is intended for. Class D
accounts for 1/16th (268,435,456) of the available IP
addresses.
Class E -
Class E is used for experimental purposes only. Like
Class D, it is different from the first three classes. It has
a first bit value of 1, second bit value of 1, third bit value
of 1 and fourth bit value of 1. The other 28 bits are used to
identify the group of computers the multicast message is
intended for. Class E accounts for 1/16th (268,435,456) of the
available IP addresses.
Private IP ranges:
10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255
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What is NTFS / FAT32?
FAT32:
The existing File Allocation Table (FAT) file system was
invented in 1977 as a way to store data on floppy disks for
Microsoft stand-alone Disk Basic. Although originally intended
for floppy disks, FAT has since been modified to be a fast,
and flexible system for managing data on both removable and
fixed media. In 1996 Windows 95 OSR2 came out with FAT32 a new
and improved FAT.
FAT32 provides the following enhancements over previous
implementations of the FAT tile system: Supports up to 2
terabytes in size
Uses space more efficiently. FAT32 uses smaller clusters (e.g.
4kb clusters for drives up to 8GB in size), resulting in up to
5% more efficient use of disk space relative to large FAT
drives. The following chart is an example of what the cluster
size would be for the various sizes of hard drives as you can
see a 32GB drive or larger will support the same cluster size
as FAT16.
NTFS:
Short for NT File System, one of the file system for the
Windows NT operating system (Windows NT also supports the FAT
file system). NTFS has features to improve reliability, such
as transaction logs to help recover from disk failures. To
control access to files, you can set permissions for
directories and/or individual files. NTFS files are not
accessible from other operating systems such as DOS.
So, which has better security, features, control and
stability?
NTFS has all those features and more. The main benefit of NTFS
is the security. You can set file and folder level permissions
to different user groups.
Some of the features you can use when you choose NTFS are:
Domains, which are part of Active Directory, and which you can
use to fine-tune security options while keeping administration
simple. Domain controllers require NTFS.
File encryption, which greatly enhances security.
Permissions that can be set on individual files and on
folders.
Sparse files. These are very large files created by
applications in such a way that only limited disk space is
needed. That is, NTFS allocates disk space only to the
portions of a file that are written to.
Remote Storage, which provides an extension to your disk space
by making removable media (such as tapes) more accessible.
Recovery logging of NTFS meta data, which helps you restore
information quickly in the event of power failure or other
system problem. This allows access to the volume immediately
after restarting the computer without waiting for chkdsk.exe
to run.
Disk quotas, which you can use to monitor and control the
amount of disk space used by individual users.
Better scalability to large drives. The maximum drive size for
NTFS is much greater than that for FAT, and as drive size
increases, performance with NTFS doesn't degrade as it does
with FAT.
You can still do all the same things that you could with the
FAT32 system.
NTFS is much faster then FAT32.
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What's the
difference between a router / switch / hub?
Hub:
Also known as a dumb hub. Hubs are general repeaters that
share bandwidth between other devices connected to it. If you
have a 100Mb hub and 4 ports, and 4 devices connected to the
hub, each device is using the same 100Mb bandwidth. So, if PC1
is pushing a large amount of files, that will slow down the
other devices connected to that hub. PC1 is using 1/2 of the
resources the hub is designed for, so, the rest of the
machines share the remaining resources. This results in poor
performance which can result in data colisions. Another down
side to a hub is that it broadcasts to each PC since it's not
smart enough to remember where each device is.
Switch:
There are two types of switches, managed and unmanaged
switches. Unmanaged switches are more common in homes and SOHO
settings. Switches are Collision detection and prevention and
each port is allocated 100Mb. Meaning each device does not
share the bandwidth resulting in faster network performance.
Router:
There are different types of routers, what will be explained
are home routers. A router is a switch that acts as a DHCP
(Dynamic Host Configuration Protocol), and sometimes a NAT
server. All that means is that it can assign any device
connected to it an IP, Subnet, Gateway and DNS servers
automatically. Usually NAT will function as a firewall between
your PC's and your internet connection.
This will make sharing an internet connection and file sharing
easier for home users who do not have a dedicated server to
function as the "router".
What's the difference between Full-duplex and half-duplex?
Full duplex allows two devices to send / receive data at the
same time, just like you can with someone on a telephone. A
good example of half-duplex is a walkie-talkie, only allowing
once device to send / receive at a time.
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What's IPv6?
IPv6 is short
for "Internet Protocol Version 6". IPv6 is the "next
generation" protocol designed by the IETF to replace the
current version Internet Protocol, IP Version 4 ("IPv4").
Most of today's internet uses IPv4, which is now nearly twenty
years old. IPv4 has been remarkably resilient in spite of its
age, but it is beginning to have problems. Most importantly,
there is a growing shortage of IPv4 addresses, which are
needed by all new machines added to the Internet.
IPv6 fixes a number of problems in IPv4, such as the limited
number of available IPv4 addresses. It also adds many
improvements to IPv4 in areas such as routing and network
auto configuration. IPv6 is expected to gradually replace IPv4,
with the two coexisting for a number of years during a
transition period.
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How do I determine
what my PC specs are?
So you have
you've always wanted to know what you have for hardware inside
your PC, but you could never figure out how to find out with
out opening up your computer. With this mini guide, we can
help you find out what hardware you have.
There are times when you may have to just go inside your case
and look around. But, for now we will describe how to
determine what you have through a few different pieces of
software.
Here's a list of freeware programs you need to download:
CPUID
Belarc Advisor
PC Wizard 2004
Sandra
These programs will give you detailed information about your
PC. A lot of it you don't really NEED to know unless your a PC
buff. These will usually give you a general idea of what you
have also.
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What is Spyware?
Spyware is Internet jargon for Advertising
Supported software (Adware). It is a way for shareware authors
to make money from a product, other than by selling it to the
users. There are several large media companies that offer them
to place banner ads in their products in exchange for a
portion of the revenue from banner sales. This way, you don't
have to pay for the software and the developers are still
getting paid. If you find the banners annoying, there is
usually an option to remove them, by paying the regular
licensing fee.
Why is it called "Spyware"?
While this may be a great concept, the downside is that the
advertising companies also install additional tracking
software on your system, which is continuously "calling home",
using your Internet connection and reports statistical data to
the "mother ship". While according to the privacy policies of
the companies, there will be no sensitive or identifying data
collected from your system and you shall remain anonymous, it
still remains the fact, that you have a "live" server sitting
on your PC that is sending information about you and your
surfing habits to a remote location...
And best of all, spy ware is not illegal.
Real spy ware...
There are also many PC surveillance tools that allow a user to
monitor all kinds of activity on a computer, ranging from
keystroke capture, snapshots, email logging, chat logging and
just about everything else. These tools are often designed for
parents, businesses and similar environments, but can be
easily abused if they are installed on your computer without
your knowledge.
These tools are perfectly legal in most places, but, just like
an ordinary tape recorder, if they are abused, they can
seriously violate your privacy.
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So how do I get
infected?
You
usually get infected because your security settings are too
low. This FAQ is mainly for Internet Explorer.
Here are a number of recommendations that will help tighten
them, and which will contribute to making you a less likely
victim:
Watch what you download!
Many freeware programs, and P2P programs like Grokster, Imesh,
Kazaa and others are amongst the most notorious, come with an
enormous amount of bundled spy ware that will eat system
resources, slow down your system, clash with other installed
software, or just plain crash your browser or even Windows
itself.
Go to IE | Tools | Windows Update | Product Updates, and
install ALL Security Updates listed.
It's important to always keep current with the latest security
fixes from Microsoft.
Install those patches for Internet Explorer, and make sure
your installation of Java VM is up-to-date. There are some
well known security bugs with Microsoft Java VM which are
exploited regularly by browser hijackers.
Go to Internet Options| Security | Internet, click "default
level", then OK.
Now press "Custom Level."
In the ActiveX section, set the first two options ("Download
signed and unsigned ActiveX controls) to 'prompt', and
'Initialize and Script ActiveX controls not marked as safe" to
'disable'.
Now you will be asked whether you want ActiveX objects to be
executed and whether you want software to be installed.
Sites that you know for sure are above suspicion can be moved
to the Trusted Zone in Internet Option/security.
So why is activex so dangerous that you have to increase the
security for it?
When your browser runs an activex control, it is running an
executable program. It's no different from double-clicking an
exe file on your hard drive.
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What is the difference between DDR and SDRAM?
SDRAM
(synchronous DRAM) has become the standard type of memory for
PCs. The main reason for this is that SDRAM is tied to the
front-side bus clock in your system. SDRAM and the bus execute
instructions at the same time rather than one of them having
to wait for the other. As bus speeds have increased beyond
100MHz, this has improved system performance.
DDR SDRAM
DDR (double data rate) memory is the next generation SDRAM.
Like
SDRAM, DDR is synchronous with the system clock. The big
difference between DDR and SDRAM memory is that DDR reads data
on both the rising and falling edges of the clock signal.
SDRAM only carries information on the rising edge of a signal.
Basically this allows the DDR module to transfer data twice as
fast as SDRAM. For example, instead of a data rate of 133MHz,
DDR memory transfers data at 266MHz.
DDR modules, like their SDRAM predecessors, are called DIMMs.
They use motherboard system designs similar to those used by
SDRAM; however, DDR is not backward compatible with
SDRAM-designed motherboards. DDR memory supports both ECC
(error correction code, typically used in servers) and
non-parity (used on desktops/laptops.)
Rambus DRAM
Rambus memory (DRAM®) is a revolutionary step from SDRAM.
It's a new memory design with changes to the bus structure and
how signals are carried. Rambus memory sends less information
on the data bus (which is 18 bits wide as opposed to the
standard 32 or 64 bits) but it sends data more frequently. It
also reads data on both the rising and falling edges of the
clock signal, as DDR does. As a result, Rambus memory is able
to achieve effective data transfer speeds of 800MHz and
higher.
Another difference with Rambus memory is that all memory slots
in the motherboard must be populated. Even if all the memory
is contained in a single module, the "unused" sockets must be
populated with a PCB, known as a continuity module, to
complete the circuit.
Rambus DRAM modules are known as RIMM modules (Rambus inline
memory modules). Rambus memory supports both ECC and non-ECC
applications.
How do DDR and Rambus memory compare performance wise? Sorry,
I know you don't want to hear this, that depends. Both
technologies have their own ardent supporters and we have seen
several different benchmarks to date that provide conflicting
results.
On the surface, it seems simple: Data flow at 800MHz is faster
than data flow at 266MHz, right? Unfortunately, it isn't that
simple. While Rambus modules may have the ability to transfer
data faster, it appears to have higher latency (the amount of
time you have to wait until data flows) than that of a DDR
system. In other words, the first data item transferred in a
Rambus transaction takes longer to initiate than the first
data item moved in a DDR system. This is due in part to how
the systems are constructed.
In a DDR or SDRAM system, each DIMM is connected, individually
and in parallel, to the data bus. So whether you have a single
DIMM or multiple DIMMs, the amount of time it takes to
initiate a data transfer is effectively unchanged.
In a Rambus system, RIMM modules are connected to the bus in a
series. The first data item transferred must pass through each
RIMM module before it reaches the bus. This makes for a much
longer distance for the signal to travel. The result is higher
latency. That's not necessarily a problem in an environment
where data transactions involve lengthy streams of data, such
as gaming. But it can become an issue in environments where
many small transactions are initiated regularly, such as a
server.
To further explain, here's an example that we can all relate
to, driving your car to the store. You can take the roundabout
freeway and drive 20 miles at 70 MPH. Or, you can take a more
direct route and drive just 5 miles at 50 MPH. You might go
faster on the freeway but you'll get to the store (Memory
Controller) faster on the straight-line route.
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How do I format my
drive?
If you
want to do a straight format, then the easiest way is to get a
Windows 98 boot disk, by either creating one in Windos 98 or
going to Bootdisk.com.
Once you have this disk, boot w/ out CD-ROM support. Once your
to the command prompt you will want to find out which drive
letter is assigned to your actual drive (boot disks sometimes
makes virtual drives). Run fdisk by typing FDISK. Delete all
of your partitions. Exit FDISK and run this command just to be
safe: fdisk /mbr
Now, go back into FDISK, create however may partitions that
you want. Exit FDISK and reboot your PC with the boot disk in
the floppy drive and boot with it w/ out CD-ROM support again.
Now, run this command format C:. Do this for all of the
partitions you created.
Later on if you created 1 partition and left extra un
allocated space and have Windows 2000 or XP, you can go into
Disk Management and create more partitions.
Remember that formatting with a 98 boot disk will format with
FAT32, not NTFS. If you want NTFS, you will have to use
Windows 2000's or XP's setup wizard to format the drive for
you after you create your partitions in the setup wizard.
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Why doesn't my hard
drive have the advertised amount of space?
When you buy 120 Gigabyte hard disk, you
will never see the size reported as 120GB. This FAQ looks at
the reason why and at the issues involved. It does not
consider the issue of file system overheads which will further
decrease the free space after formatting.
I'm sure that at some point someone has told you that a
Kilobyte is 1024 Bytes. If we are pedantic about the
terminology used in describing storage however, they are
wrong. A Kilobyte is by definition 1000 bytes, Kilo literally
denoting 10^3 of something. What they are talking about is, in
fact, a Kibibyte (2^10 Bytes.) This inconsistency causes
problems because when people start talking about computer
storage - Kilo is suddenly used incorrectly to mean "2^10"
rather than the proper "10^3."
Here Follows a quick terminology break:
Giga- A Prefix meaning 1 Billion, or 10^9 of something.
Kilo- A Prefix meaning 1 Thousand, or 10^3 of something.
Gibi- A Prefix meaning 2^30 of something, derived from
Gigabinary.
Kibi- A Prefix meaning 2^10 of something, derived from
Kilobinary.
Equivalents for Mega-, Tera-, Peta-, etc. all exist in similar
fashion.
While this seems a little fussy, it becomes important when
talking about large quantities. The difference between a
Kilobyte and a Kibibyte is 24 bytes (2^10 - 10^3,) an amount
very few people are going to notice or care about. When we
start looking at Gigabytes and Gibibytes however, the
difference is 73,741,834 Bytes (2^30 - 10^9,) a significant
quantity.
It naturally follows that as quantities get larger, this
discrepancy increases. 120 Gigabytes translates to
approximately 112 Gibibytes so naturally people feel cheated
after formatting their new storage monster and finding less
space than they expect. The amount in Gibibytes (and thus the
amount of space that will be reported) can be calculated as
follows:
Storage in Gibibytes = (Storage in Gigabytes)*(10^9)/(2^30)
So why don't hard drive manufacturers rate their drives in
Gibibytes? Bizarrely enough, one pressing reason is to avoid
confusing consumers. There have been movements to see KiB, MiB
and GiB units introduced in storage to represent Kibibytes,
Mibibytes and Gibibytes respectively. This would require
re-branding of any products rated in the base 10 system as
well as re-education of the end user. Marketing also comes
into the equation as drive sizes increase. The first company
to make the switch to Gibibytes would suddenly have a range of
products that look smaller than their base 10 equivalents.
In the end, consistency is the most important point. Two
different 120 Gigabyte drives are going to be almost exactly
the same size regardless of manufacturer or model. The reasons
for changing to a base 2 system simply aren't pressing enough
to warrant the problems of doing so. It's a little annoying,
but two minutes with a calculator will verify that 111.7 Gigs
is, in fact, the correct amount of space for a 120 Gigabyte
drive to be reporting.
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How do I disable
Windows Messenger Service?
Disabling
the Messenger Service
To disable the sometimes annoying WMS popups follow these
instructions:
Windows XP Professional
Click Start | Settings | Control Panel
Click Administrative Tools
Click Services
Double click Services
Scrolldown and highlight "Messenger"
Right click the highlighted line and choose Properties
Click the STOP button
Select Disable or Manual in the Startup Type scroll bar
Click OK
Windows 2000
Click Start | Settings | Control Panel | Administrative Tools
| Services
Scroll down and highlight "Messenger"
Right click the highlighted line and choose Properties
Click the STOP button
Select Disable or Manual in the Startup Type scroll bar
Click OK
Windows NT
Click Start | Control Panel
Double Click Administrative Tools
In the Messenger Properties window, select Stop
Then choose Disable as the Startup Type
Click OK
Windows 98 & ME
Windows Messenger Service cannot be disabled unfortunately
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What is Dual-Channel DDR?
A
processor in a computer is like the engine of a car. A car
needs gas to fuel its engine. Similarly, a computer CPU needs
memory storage to process its data. Data must be stored in
memory first, before being delivered to the processor. When
more data can delivered to the CPU via memory at faster
speeds, the CPU can manipulate instructions and data more
efficiently and ultimately, the requested task can be
accomplished in less time.
Data is filled into a funnel (memory); the funnel then
channels the data through its pipe to the CPU's input.
Dual-Channel memory utilizes two funnels and two pipes to feed
data to the CPU, thereby being able to deliver up to twice the
data of a single fennel. With two channels and funnels, data
is transferred 128 bits at a time. The process works the same
way when data is emptied from the CPU by reversing the flow of
data. To prevent the funnel from being over filled with data
or to reverse the flow of data through the funnel, here is a
traffic controller shown as a valve on the funnels pipe. On
your motherboard, there's a chip called a memory controller
that handles all data transfers involving the memory modules
and the CPU.
With dual channel memory, the memory controller is able to
move double the peak amount of data that it could normally
move with single channel memory. That's because it is sending
or receiving data from the two memory module pairs at the same
time.
Color depths and what
they mean?
Here's a general break down of the
different color depths:
Color Depth Guide 32-bit 16.7+million colors plus an 8-bit
(256-level) grayscale mask.
24-bit 16.7+million colors
16-bit 65.5 thousand colors
15-bit 32.8 thousand colors
8-bit 256 colors
7-bit 128 colors
6-bit 64 colors
5-bit 32 colors
4-bit 16 colors
3-bit 8 colors
2-bit 4 colors
1-bit 2 colors
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DVD-RW/R | DVD+RW/R ?
So what's
the difference between DVD-R / -RW & DVD+R / +RW?
DVD-R / -RW
The originating DVD format that was compatible with most DVD
players is DVD-R/RW. DVD-R/RW supports both single-sided (4.7
GB) and double-sided (9.4 GB) media. Due to the amount of time
that DVD-R/RW has been out, many more stand alone DVD player
are likely to support them. This format is pretty much your
everyday use format. It is advised to use this format if you
intend to create home movies, and other applications that
would run from a stand-alone DVD player.
DVD+R / +RW
The new format is DVD+R/RW, which happens to be based on CD-RW
technology. This format is becoming increasingly popular. The
compatibility rate of this format however is not as high as
the older format on stand-alone players. The introduction of
the DVD+R/RW was created in the intent that the format would
be completely compatible across both DVD optical drives in
computers, and drives in stand-alone players. The format also
allows for a mix of information on the media, such as not only
video, but also data files. This is not to say that the
previous format cannot be used for data, it is just to say
that the creators of this format felt DVD+R/RW was a much
better format to be used for both purposes. The DVD+R/RW
format supports both CAV and CLV writing as well as lossless
linking. CAV is an acronym for Constant Angular Velocity. This
feature pretty much means that the data transfers at the same
speed regardless of where it is being read off the disc; as
opposed to Constant Linear Velocity which is dependant on the
location of the disc being read. CLV is the method of transfer
used by most of the older optical drives. The introduction of
CAV allows the drive unit to operate without much trouble as
it does not have to regulate the motor speed. This is an
improvement over CLV which can run into problems on higher
speed optical devices because of the brief latency when
changing motor speed. Currently most DVD+R media are capable
of writing at a maximum of 8x where as DVD-R is still at a 4x
specification.
Over all, DVD+ RW / R is best to be used for computers as it's
read times / write times are faster. If you want to distribute
your videos to DVD players in your living room, it's best as
of now (early 2004) to use DVD-RW / R for this. Personally
myself, I will use the + format since I only use my DVD discs
for data.
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What is is the OSI model?
What is OSI and
how important is it? OSI stands for Open Systems Interconnect.
It is how every network "aware" application, NIC, switch,
whether it's a managed or unmanaged switch, hub, router,
firewall, etc communicates which the OS and each other.
The OSI model has 7 layers to it and each play an important
role. Here are the layers in order:
Application
Presentation
Session
Transport
Network
Data-link
Physical
A very easy way to remember this is All People Seem To Need
Data Processing. Here's an image of the OSI layer that may
help as well:
Networking consists of basically sending data from one device
to another. The sending PC must recognize the data, divide the
data into manageable chunks, add info to each chunk to
determine the destination and who can receive the data, add
timing and error checking information to ensure the data is
received the way it was sent, and finally pushes the data out.
The receiving PC will do the opposite of the sender, it will
take the data off the link, and processes it from 7-1 so to
speak.
Each layer when sending or receiving does something different
to each packet and passes it to the next layer.
Now, I'll give an overview of each layer's function.
Application layer:
Topmost layer of the OS Model. This layer relates to
applications / services that support user apps, FTP,
databases, email, chatting, etc.
Presentation layer:
Format that is used to exchange data among networked devices.
Such as IBM - Apple - Sun. So, data that is received from the
Application layer is transformed into a common language.
Session Layer:
Allows two apps to open, use and close sessions to communicate
with each other. This layer handles the security, it puts
checkpoints in the data stream. They break data into smaller
groups, so if data is lost at one check point, only the data
from that checkpoint is resent.
Transport Layer:
This layer works with the session layer ensuring that there is
no data loss and that everything is sent in tact.
The sending device at this layer repackages messages, dividing
long messages into smaller packets and collecting small
packets together in one package. This ensures packets are
transmitted efficiently. The device receiving the packets
reassembles the original messages and sends an acknowledgment
that it was received. This is the layer that TCP and SPX
reside.
Network Layer:
This layer is responsible for addressing messages and
translating logical addresses and names into physical address.
Determines the route from the source to the destination
computer. Determines which path is best for the data to follow
on a network. It handles traffic problems and data priority as
well. If the port on the router cannot transmit a data chunk
as large as the source sends, this layer will compensates for
breaking the data into smaller units. The receiving end
reassembles the data. This layer is where IP and IPX reside.
Data-link Layer:
This layer sends data frames from the network layer to the
physical layer. It controls the electrical pulses that enter
and leave the physical layer. On the receiving end, this layer
repackages the signals from the physical layer back into data
frames.
Here's an example of a data packet:
Bit patters tokens and encoding methods are known to this
layer.
This layer is responsible for error free transfer of these
frames from one device to another through the physical layer.
Physical Layer:
This layer is responsible for transmitting the rata data
packets over a physical medium or wireless medium.
This layer also synchronizes bits and encoding. This layer is
the physical layer on which it decides how data is sent
through a NIC port, switch and media (CAT5, BNC, wireless,
etc).
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