Browse Prior Art Database

Increased Direct Access Storage Device Yield through Defective Track Handling in Hardware

IP.com Disclosure Number: IPCOM000052594D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Ganguly, A: AUTHOR [+2]

Abstract

Disk packs with relatively large amounts of defective tracks can be use in the present technique, increasing the manufacturing yield and easing the manufacturing process to achieve the highest possible yield.

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Increased Direct Access Storage Device Yield through Defective Track Handling in Hardware

Disk packs with relatively large amounts of defective tracks can be use in the present technique, increasing the manufacturing yield and easing the manufacturing process to achieve the highest possible yield.

In the current Count-Key-Data (CKD) Direct-Access Storage Device (DASD), the defective/alternate track handling has a severe impact on the performance of the DASD accesses, primarily due to the time consuming access arm movement to and from the alternate track. For this reason, there is always a desire to keep the number of defective tracks low, if not even zero.

In the following, a scheme is described where the device hardware performs the defective/alternate track handling with only minor impact on the performance of the given access.

For each device, a table is implemented (e.g., an alterable read-only memory) which allows a fast translation from logical to physical track address (Fig. 1). See Original Page 625

The table look-up is performed when the control unit does two functions: 1. Issue a seek command

In this case, the device logic will translate the logical cylinder (CYL) and head (HD) value from the seek argument into the physical (actual) CYJ, HD value read from the table. Then the physical CYL, HD value is used to perform the access arm movement and later the head selection. 2. Issue a head switch

Here again the device electronics will get the physical track...