30-03-2012, 11:23 AM
computer hardware
hardware.ppt (Size: 181.5 KB / Downloads: 146)
basic components
basic components are
processor
memory
motherboard
input/output devices
disks
network interfaces
The first three, plus the bus speed, are essential to the understanding of the performance of the computer.
processors
The processor does all the calculations on a computer.
The performance indicator of the processor is the frequency of operations.
There are various types of processors, by different manufactures.
Intel
AMD
architecture
The Debian operating system offers a complete range of software that can be run with a range of processors by a certain manifactures. Such a range of software packages is called an architecture.
We use the i386 architecture for Intel processors.
AMD processors may be more open source friendly
memory
The memory is where all data that the computer works with is stored.
If the memory is small the computer has to perform more operations to read and write data to the disk.
As a consequence, it will appear to be slower.
motherboard
This is a green sheet of plastic that all components inside the computer attach to.
We don't need to know more about it, just the plane concept will do.
devices
These are things that the computer uses for input and output of data.
Examples include
keyboard
screen
network card
disks
We only need to study disks and network cards.
disks
There are three architectures of disks
IDE, aka PATA, an old system
SCSI, a bit more modern
SATA, used in most modern systems
We need to be aware of them because the way that Linux refers to them.
IDE
When a computer can use IDE, you see two forty-pin connectors on the motherboard.
These are the primary and the secondary IDE channnels. They are usually labelled.
To each channel, you can attach two disks.
One is called the master.
The other is called the slave.
master and slave
One method to select master and slave is to set jumpers on the disk. The position of the jumpers is often written on the disk. Otherwise
The other method is called “cable select”. There you place the master at the end of the 40 pin IDE cable.
device names
Linux needs to give the devices names in other to talk to them.
The device names for IDE are
/dev/hda for the primary master
/dev/hdb for the primary slave
/dev/hdc for the secondary master
/dev/hdd for the secondary slave
SCSI and SATA
SCSI and SATA drives are named
/dev/sda
/dev/sdb
etc.
Usually it is a bit of guesswork to know which drive is give what name. There may be a better way than guesswork, but I don't know about it.
file systems
A file system is a way to set up files on a disk.
Common file systems are
Microsoft FAT
ext2 or ext3, used in Linux
Reiserfs, used on Linux
Linux kernels support various file systems natively, including Microsoft file systems.
several file systems
If you have several file systems on a disk, each system needs to occupy a separate physical area on the disk.
Such an aera is called a partition.
An empty disk will have no partitions.
You will have to set up partitions before working with a disk.
Chaning the partitions at a later stage will, generally, make the data on the disk inaccssible.
partition table
Any disk has a special place for the partition table.
The partition tables says
what partitions are on the disk,
where each partition starts and end
Changing the partition table makes all data on the disk unusable.
default partitions
On a Linux system, if you only have one disk on a computer, it is customary to have two partitions on it.
the main data partition
the swap partition
Deciding on the size of both is a bit of black magic. There is no hard rule.
We let the Debian installer do it for us.
device names with partitions
If you have a device that linux calls foo, the first partion will be foo1, the second partition will be foo2 etc.
Thus you can have /dev/hda1, /dev/sdb3 etc.
The command “df” will list all devies and all partition.
the main data partition
This is where you have all the data on the hard disk.
This is usually formatted with the ext3 file system.
There other file systems one could use, but this is the default, one and we will use that one.
the swap partition
The swap partition is used to reserve space for swapping.
Swapping is a way for a computer to work with large memory requirements by writing parts of the memory on the disk.
When this happens the computer appears to be very slow.