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  1. 2011/09/16(金) 16:48:09|
  2. Huetay|
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1 head hard disk drive internal structure of the head is the most expensive components, but also the hard drive technology is the most important and most critical part.


Read-write head is the traditional unity of the electromagnetic induction type head, but the hard drive reading and writing but are two different operations, for which the head of this combo in the design must also take into account the read / write two characteristics,picture change
resulting in a hard to design limitations. The MR head (Magnetoresistive heads), the magnetoresistive head, using the detachable head structure: write heads are still using the traditional magnetic head (MR head can not write), the read head is used a new type of MR heads, the so-called induction write, magnetoresistive read.


Thus, in the design can be different for the two properties were optimized to get the best read / write performance. In addition, MR head resistance change, rather than through changes to the current sense signal amplitude, and thus very sensitive to signal changes to read data accuracy have been increased. And because the signal amplitude reading has nothing to do with the track width,surge protector
so the track can be made very narrow, thereby increasing the areal density, to achieve 200MB / inch 2, which can only be achieved using traditional head 20MB / inch 2, which is the MR head the most important reason is widely used. Currently, MR head has been widely used, while the use of magnetoresistive effect multi-layer structure and the production of better materials GMR head (Giant Magnetoresistive heads) are also becoming more common.


2 track when the disk rotates, the head if maintained at a position on each surface of the disk head will draw a circular path,logical component
the path is called circular track. These tracks can not see with the naked eye, because they are only magnetic disk in a special way on a number of magnetized areas on the disk information is stored along this track. Between adjacent tracks is not next, this is because the magnetic element away from too close to each other when the magnetic effect, but also difficult to read and write heads.


A 3.5-inch 1.44MB floppy disk, one side has 80 tracks, the track density on the hard disk is far greater than this value, usually one side there are thousands of tracks. 3 sectors on the disk so each track is divided into several arcs, these arcs is the disk sectors, each sector can store 512 bytes of information, the disk drive reads and to disk write data to the sector as a unit.哮喘
1.44MB3.5-inch floppy disk, each track is divided into 18 sectors.


4 cylinder hard drive is usually a set of overlapping disks, each of the disk are divided into an equal number of tracks, and from the outer edge of the "0" number, with the same number of tracks form a cylinder, called the disk cylinder. The number of cylinders and a disk drive the number of tracks on one side are equal. Whether single or double disk disk, because each disk has its own head, so the disk is equal to the total number of heads. The so-called hard disk CHS, the Cylinder (cylinder), Head (heads), Sector (Sector), as long as the CHS to know the number of hard disk, you can determine the capacity of the hard disk, hard disk capacity = cylinders * heads, * number of sectors * 512B.


Basic Int 13H call BIOS Int 13H calls are provided by the BIOS basic input output interrupt calls the disk, it can complete the disk (including disk and floppy disk) is reset, read and write, check, location, diagnosis, formatting and other functions.


It uses CHS addressing is, the maximum knowledge about access to 8 GB hard drive (if not for this article, special instructions, are 1M = 1048576 bytes). Modern hard disk drives in the old structure, because the same number of sectors per track, so the heretics of the recording density is much lower than within the channel, so it will waste a lot of disk space (and floppy disk).


To solve this problem, to further improve the hard disk capacity, it is hard to switch to other density structure of the production. In other words, outer tracks than inner tracks and more sectors, using this structure, the hard drive no longer has the actual 3D parameters, addressing ways to linear addressing, which is addressed in sectors .


In order to address the old with the use of 3D software is compatible (such as the use BIOSInt13H interface software), the hard disk controller installed within an address translator, which is responsible for the translation into the new old-fashioned 3D parametric linear parameters. This is why the 3D parameters can now drive a wide selection of reasons (different modes, corresponding to different 3D parameters, such as the LBA, LARGE, NORMAL).


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