R/W Multiple Mode

This mode is implemented per ANSI ATA/ATAPI-4 specification. Read/Write Multiple allows the host to transfer a set number of sectors without an interrupt request between them, reducing transfer process overhead and improving host performance.

 

Random Access Memory (RAM)

Memory designed so that any storage location can be accessed randomly, directly and individually. This is contrasted to sequential access devices such as tape drives.

 

Read

To access a storage location and obtain previously recorded data. To sense the presence of flux reversals on magnetic media. Usually implemented such that a dynamic flux amplitude will cause a proportional electrical output from the transducer.

 

Read Ahead Mode

A mode of operation of a disk drive. Following a read request, drive read-ahead begins on the first sector and continues sequentially until the allocated buffer is full. If a read request is received during the read-ahead operation, the buffer is examined to determined if the request is in the cache. If a cache hit occurs, read-ahead mode continues without interruption and the host transfer begins immediatly.

 

Read Gate Signal

A digital input signal level which causes the drive circuitry to recover data.

 

Read Only Memory (ROM)

A form of memory which cannot be changed in formal operational modes. Many different types are available. RAM used for permanent information storage. Computer control programs are often stored in ROM.

 

Read/Write Head

The recording element which writes data to the magnetic media and reads recorded data from the media.

 

Re-Calibrate

The action of moving the head of a disk drive to cylinder zero.

 

Recoverable Error

A read error, transient or otherwise, falling within the capability of an ECC mechanism to correct, or able to overcome by rereading the data in question.

 

Rotational Latency

The amount of delay in obtaining information from a disk drive attributable to the rotation of the disk.

 

Run-Length Limited

An encoding process that repositions data bits and limits the length of string of zero bits in order to compress information being stored on disks.

 

Run-Length Limited (RLL) Encoding

A recording code. Various types exist with different efficiencies. Sometimes meant to denote "2.7 RLL" which can signify 1.5 times the bits as MFM, given the same number of flux reversals in a given lineal distance.