Term

Definition

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grin

<vbg>

very big grin

Actuator

The assembly inside a disk drive that holds the heads and moves them back and forth over the disks.

AGC

Automatic Gain Control - preset for each head and each zone--yet another thing in the tables of data in the "hidden" tracks outside of Track 0. Some disk surfaces are "hotter" than others, and some heads are more sensitive than others. AGC makes it possible to send a fairly consistent signal between the preamp and the main read/write chip on the circuit board. It's convenient to have a stored value for automatically pre-setting the AGC level--then the circuits can fine-tune from there. You could think of it as another scheme to reduce soft error rates.

Aliasing

A type of noise which occurs when a sampled signal contains frequencies which are more than half the sampling device's input sampling frequency. "False frequencies".

ASIC

Application Specific Integrated Circuit

ATA

see IDE

ATAPI

AT Attachment Packet Interface (part of the E-IDE spec).

CD

compact disc - a family of optical storage (e.g. CD (audio),

CD-ROM, CD-R, CD-i, CD-R/W, and so forth). These CD members are associated with the "red book", "yellow book", "green book", and "orange book" standards

CRC

Cyclic Redundancy Check

DSP

Digital Signal Processor

DVD

Digital Versatile Disk

ECC

Error Correcting Code

EE

Electrical Engineer

E-IDE

Known as Fast IDE or ATA-2 and includes support for tape and CD-ROM drives. Created and promoted by Western Digital

EMF

ElectroMotive Force

EMI

ElectroMagnetic Interference

FAT

File Allocation Table

FET

Field Effect Transistor

GB

GigaByte

GMR

Giant MagnetoResistive

ICE

In-Circuit Emulator : A tool (debugging) that emulates the processor on your target system.

ID

header information for a data sector which includes track, sector number, head and CRC information. There is a ID-less recording format which eliminates this header information from the data sector.

IDE

Integrated Drive Electronics defined by Western Digital and Compaq

IEEE

Institute of Electrical and Electronics Engineers

Interface Data Rate

how fast data can be transferred between the host and the disk drive over its interface

MB

MegaByte

MB/s

MegaBytes per second

ME

Mechanical Engineer

Media Data Rate

how fast data can be transferred to and from the media

MFM

Modified Frequency Modulation

MO

Magneto-Optical

MR

MagnetoResistive

MRX

eXtended MagnetoResistive

Nyquist Theorem

The principle explaining the manner in which aliasing is produced. One half the sampling frequency of any device -- the point above which aliasing is produced -- is often referred to as the Nyquist frequency of that device.

OEM

Original Equipment Manufacturer

PCBA

Printed Circuit Board Assembly

PLL

Phase Locked Loop - timing information is in the data stream and is used to set the receiver's local clock

PRML

Partial Response, Maximum Likelihood - is the currently popular method of decoding the analog data that the head reads. Also comically known as “Pretty Risky, Maybe Lucky”

RFI

Radio Frequency Interference

RLL

Run Length Limited

RPM

Revolutions Per Minute

R/W

Read/Write

SCSI

Small Computer System Interface

SI

System International. In SI units the standard length is the meter, that for time is the second, and that for mass is the kilogram.

SST

Super Sonic Transport (e.g. British Airways' Concorde)

Striping

Storing information on multiple disk drives by splitting up the information and accessing all of the drives in parallel.

Stroke

The distance across the disk that the heads can move

TMR

Track MisRegistration

TPI

Tracks Per Inch

UL

Underwriters Laboratories a private company that creates safety standards and then charges companies to test their products

VCM

Voice Coil Motor