An ordered collection of information. In a specific case, it is the information processed by a computer.
Average data error rate allowed with all error recovery features activated.
An electronic circuit which decodes playback data and produces separate clock and data bits.
Sometimes incorrectly used to denote data synchronizer.
An electronic circuit producing a clock signal that is synchronous with the incoming data
stream. This clock signal is then used to decode the recording code being used into user data.
DATA TRANSFER RATE
In a disk or tape drive, the rate at which data is transferred to or from the storage media.
It is usually given in thousands of bits per second (Kbit/second) or millions of bits per
second (Mbit/second). See: PIO, DMA or
Ultra-DMA for more detail.
DEDICATED LANDING ZONE
A designated radial zone on the disk where contact starting and stopping occur by design.
A servo scheme in which a prerecorded pattern on an otherwise unused disk surface provides
position information to the servo circuitry by means of a head reading that surface.
A magnetic imperfection in a recording surface.
A general methodology of avoiding data errors on a recording surface by avoiding the use of
known bad areas of media. Usually defective sectors or tracks are retired and data are
written in alternate locations. Several algorithms are possible such as "sector slipping",
or "spare sector per track".
A list of defects that fall within a pass/fail criteria of a user. This list is usually used
by an operating system or a disk drive controller for defect management.
A defect management scheme for avoiding surface defects. It has data written before and
after the defect, instead of using alternate tracks or sectors to avoid use of the defective area.
Generally, recording density. See areal,
bit, and storage density.
The method of erasing a track using a DC write/erase current through either a Read/Write or
Any system that processes digital binary signals (having only values of a 1 or 0; usually
in bits and bytes) rather than analog signals (signals that can have many values).
DIGITAL MAGNETIC RECORDING
See magnetic recording.
DIGITAL SIGNAL PROCESSOR (DSP)
DSP is a technology unique to Maxtor Hard Drives. Maxtor's Digital Signal Processor (DSP)
based electronics design was developed in cooperation with Texas Instruments. This is the industry's first DSP based
architecture to feature a uniprocessor that can interface both with the controller and the drive processor.
Access directly to memory location. (See Random Access Memory).
DIRECT MEMORY ACCESS
A means of data transfer between the device and host memory without processor intervention. There are two DMA modes, Single
and Multi-Word or (PIO Mode). Since single word is slower than PIO mode, it is no longer used and will be not be referred
to here. Multi Word DMA is used in EISA, VLB, and PCI equipped systems, which are capable of very fast transfer rates,
utilizing cycle times of 480ns or faster. The current ATA specification limit is 150ns. DMA eliminates the CPU from the
- The system specifies where the data transfer is to begin, and how many sectors to transfer.
- The system sends a Read/Write DMA command to transfer data.
- The drive asserts DERQ to signify it is ready to transfer data.
- The DMA controller asserts DACK- to indicate the bus is free to transfer data, and enables the memory address where the data needs to either come from or go to.
- When IOR- or IOW- are asserted, the drive transmits or receives a word of data.
- If the next word of data is ready to be transmitted or received, step 5 is repeated. If the data is not ready, the following occurs:
- The drive negates DREQ and tells the DMA controller to temporarily halt the data transfer.
- The DMA controller responds by negating DACK- and freeing up the bus to the CPU. Once the drive is ready to proceed, the process returns to step 3.
- Once the entire data transfer is complete, the drive issues an interrupt to tell the CPU the data is where it belongs.
A listing of files maintained by the disk operation system (DOS) or a data base management system to enable a user to quickly access data files.
A flat, circular piece of metal (usually aluminum) or plastic (usually mylar) with a magnetic coating upon which information can be recorded. (As an example, a
floppy disk or Winchester drive).
DISK DRIVE OR DISK MEMORY DEVICE
The total electromechanical storage device (hard disk drive) that contains disks, read/write heads, a head positioning mechanism, drive motor, and electronics.
A number of metal disks packaged in a canister for removal from the disk drive (predecessor to Winchester technology).
DISK OPERATING SYSTEM (DOS)
The software package developed to operate the computer and schedules tasks, allocate computer system resources, controls access to mass storage devices, manage files, etcetera.
Typical disk operating systems include CP/M, MS-DOS, Windows and UNIX.
Auxiliary memory system containing disk drives.
DISK TRANSFER RATE
The rate that digital data is transferred from one point to another. Expressed in either bits per second or bytes per second.
DOUBLE FREQUENCY ENCODING
Double Frequency Encoding is another name for FM encoding. This is due to the fact that all possible data combinations will result in only two possible temporal displacements of adjacent data bits, specifically "1F" and "2F".