MEMORY
IDEA BEHIND BIOS
ROM-BIOS It is short form for read only memory -basic input output system. The ROM-BIOS is a set of Program built into the computer ROM memory that Provides the most basic, low level and intimate control And supervision operation for the computer.
=>The task of the bios is to take care of the immediate needs of the hardware and to isolate all other programs from the details of how the hardware works.
=>fundamentally the bios is an interface a connection and a Translator between the computer hardware and the software Programs.
PARTS OF BIOS
There are three main part of the ROM-bios program.
First part:-
This part is used only when the computer is first turned ON; these are Test and Initialization program that check to see that the computer is working. The delay between powering on the computer and The moment when it start working for you is due to running of these test and initialization program which sometimes are Called the POWER ON SELF TEST (POST).
Second part:-
Important parts of the bios are its routimes.These programs provides the detailed and intimate control of The various part of the computer, particularly for the input/output Peripherals, such as the disk drives.
Third part:-
Rom-bios are the boot strap loader program.
Basic content of bios:
1. Standard CMOS feature.
2. Advanced bios feature.
3. Advanced chipset feature.
4. Integrated peripherals.
5. Power management setup.
6. PnP /PCI configuration.
7. Pc health status.
8. Frequency/voltage control.
9. Load optimized default.
10. Set supervisor password.
11. Set user password.
12. Save & exit setup.
13. Exit without saving.
Booting:-
The time duration between the appearance of the dos prompt or any window and the switch on the power supply the whole process is known as the booting process.
TYPE OF BOOTING
A) COLD BOOTING
B) WARM BOOTING
COLD BOOTING:-
When we switch off the computer completely and properly after some time we start Computer again is known as the cold booting.
WARM BOOTING:-
When we restart the computer from the restart button or using the key by simply pressing them i.e. ctrl+alt+del key is known as warm Booting.
MINIMUM REQUIREMENT FOR BOOTING:
For booting we required minimum three files-
1) ms_dos.sys
2) io.sys
3) Command.com
In these files first two files are hidden files and the third one is normal file.
MOTHERBOARD
If the CPU is the heart of the system the motherboard is its circulatory system. The CPU has to be fitted on the socket on the Board. The board has input output ports, ram, PCI slots, IDE port, chipset, Power connector, AGP slot, other expansion slots, floppy port.
The key features of the motherboard.
1. Socket
2. memory support
3. expansion slots
4. onboard IDE channels
5. Power supply and Power management
6. chipset
7. BIOS
8. Battery
9. Input/output ports.
SECONDARY STORAGE DEVICE
HARD DISK DRIVE
Hard disk are thin but rigid metal platters covered with a substances That allows data to be held in the form of magnetized spots. Hard disk are Tightly sealed within an enclosed hard disk drive unit to prevent any foreign Matter from getting inside Data may be recorded on both sides of the disk Platters. These platters are made of either using glass or aluminum.
A head crash happens when the surface of the read write head or particles on its surface come into contact within the surface of the hard disk platter, causing the loss of some or all of the data on the disk.
Both EIDE(enhanced integrated device electronics) and SCSI(small computer System interface) disks suffer from the limit of 1024 cylinder. The difficulty is that the old CHS (cylinder/head/sector) addressing mode uses a 10 bit number can hold a value of between 0 and 1023 , So the number of cylinders accessible by the BIOS is limited to 1024 hard disk performance measurements are-
(1) disk head seek time
(2) data transfer rate
(3) disk’s cache size.
Disk head seek time
Time taken to seek the data by move the head is referred as the seek time. The seek Time measurement that’s most often used is the average seek time, which is the average time move the head from one location to a randomly selected other location.
Another measurement closely related to seek time involves a second component beyond the head movement latency ‘Latency’ is the time it takes the desired sector to come up under the read/write head after a seek operation and average out to half the time it takes for a rotation of the disk platter. The combination of seek time and latency is known as access time. Seek time, latency , and access lime are all measured in milliseconds. Seek time of 5ms-10ms and spin at 5400 and 10000 Rpm( lower latencies being associated with higher spin rates.)
DISK TRANSFER RATE
This simply means how quickly the disk can transfer data to and from the computer. The disk spins at the same rate no matter what cylinder is being read, but modern hard drive design place more sectors along outer cylinder than along inner ones. This means that data read from the outer cylinder transfer faster than to data read from inner cylinders. Hence the internal data rate is variable.
DISK SPIN RATE
The faster a hard disk spins, the faster it can transfer data for this reason manufactures speed up spin rate now a days 10000 rpm hard disk an popular
7,200 rpm HDD - Baracuda hard disk
10,000 rpm HDD - Cheetah hard disk
A drive with fewer cylinders but more sectors per cylinder faster than one with more cylinders and fewer sectors per cylinder, all other things being equal.
HEAT GENERATION AND DISSIPATION.
As hard drives have spun faster they are developed increasing problems with heat. The faster spin rate produce increased heat and from friction and from the increased demands placed on electronic circuits that process the data. The most common method of providing extra cooling to extra hot drives cooling fan to your system. These device mount in a 5.25 Inch drive bay and allow to mount a 3.5 inch drive within adapter rails the front bezel incorporates two or three small fans that blow air onto the hard disk.
DISK CACHE SIZE
All modern hard drives incorporate a disk cache typically between 512kb and 2mb in size. This cache is composed of RAM chips. Most Operating systems including LINUX maintain their own disk Cache in computer’s RAM this is more faster. In case of LINUX the disk cache can grow and shrink as necessary.
FLOPPY DISK DRIVE
A floppy disk drive is a storage device that stores data on removable 3.5inch diameter diskettes These are encased in hard plastic but the mylar disk inside flexible or floppy Each can store 1.44 million Bytes(characters) or more of data. Floppy disk have a ‘Write protect notch’ which allows you to prevent a diskette from being written to. On the diskette data is recorded in concentrics circres called tracks.
OPTICAL DISKS: CDs AND DVDs
An optical disk is a removable disk, usually 4.75 inches in diameter and less than one twentieth of an inch thick on which data is written and read through
the use of laser beams.To read the data, a low power laser light seams the disk surface: pitted areas are not reflected and are interpreted as 0 bits, smooth areas are reflected and are interpreted as 1 bits.
CD-ROM(Compact disc read only memoly)
It only reads a CD and cannot after its contents A CD-ROM disk capacity is 650 mb -750mb the speed of a cd is read in x eg.’52x’ , which menas -> 1x=150 kb/s of transfer rate, so 44x gives 6600 kb persecond.
CD-R(Compact disk recordable)
The disk can be written once but can be read many times.
CD-RW(compact disk rewritable)
This is an erasable optical disk allows user to record and erase data so that the disk can be used over and over again CD-RW disks can not be read by CD-ROM.