Browse Prior Art Database

Disk File Sequential Access Method

IP.com Disclosure Number: IPCOM000097594D
Original Publication Date: 1961-Mar-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Sippel, RJ: AUTHOR

Abstract

This is a method of reducing the access time to information on a magnetic disk storage device 50. It is applicable where information is to be either read in or out of a 50 sequentially but not continuously.

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Disk File Sequential Access Method

This is a method of reducing the access time to information on a magnetic disk storage device 50. It is applicable where information is to be either read in or out of a 50 sequentially but not continuously.

Disk 50 has a single read-write head 52 for each of its inner tracks 54 and a plurality of read-write heads 56 for the outermost track 58. Track 58 is used as a buffer storage for information passing between the computer and the other tracks of 50.

When it is desired to read information into a particular position on a track 54 of 50, it is not necessary to wait until this position comes under the single head
52. Instead, the head 56 on track 58, which the desired position will be passing, next is selected. When the position on track 58 adjacent the desired position on track 54 comes under the selected head 56, writing starts. When 50 has advanced to the point

where the desired position on track 54 is under its head 52, the information is read from track 58 and written into track 54. This transfer of information continues until all information stored in track 58 is transferred. Where discrete bits of information are being read into 50, the next bit of information is read into track 58 at the position next to the one at which the last bit of information ends. It is therefore possible for new bits of information to be recorded on track 58 while information previously recorded is being transferred to a track 54. When one track 54 has been filled, the information is transferred to a second track 54 and so on in succession. When the last track 54 on disk 50 has been filled, there is a time lag until heads 52 can be positioned to the next disk.

A similar procedure is followed when reading out of disk 50. The information is first transferred from a track 54 to track 58, and is then read from 58 by the closest head 56 when the computer desires the information.

A sector counting method is used to control the transfer of d...