User manual MAXTOR D740X-6L 09-19-2001

[. . . ] Printed in U. S. A. This publication could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein ­ which will be incorporated in revised editions of the publication. Maxtor may make changes or improvements in the product(s) described in this publication at any time and without notice. UL/CSA/VDE/TUV UL standard 1954 recognition granted under File No. LR49896 TUV Rheinland EN 60 950 Tested to FCC Rules for Radiated and Conducted Emissions, Part 15, Sub Part J, for Class-B Equipment. PATENTS These products are covered by or licensed under one or more of the following U. S. [. . . ] With this feature, the buffer space used for read and write operations is dynamically allocated. The cache can be flexibly divided into several segments under program control. A cache entry consists of the requested read data plus its corresponding prefetch data. Adaptive segmentation allows the drive to make optimum use of the buffer. The amount of stored data can be increased. DisCache anticipates host-system requests for data and stores that data for faster access. When the host requests a particular segment of data, the caching feature uses a prefetch strategy to "look ahead", and automatically store the subsequent data from the disk into high-speed RAM. If the host requests this subsequent data, the RAM is accessed rather than the disk. Since typically 50 percent or more of all disk requests are sequential, there is a high probability that subsequent data requested will be in the cache. This cached data can be retrieved in microseconds rather than milliseconds. As a result, DisCache can provide substantial time savings during at least half of all disk requests. In these instances, DisCache could save most of the disk transaction time by eliminating the seek and rotational latency delays that dominate the typical disk transaction. For example, in a 1K data transfer, these delays make up to 90 percent of the elapsed time. DisCache works by continuing to fill its cache memory with adjacent data after Maxtor D740X-6L 20. 0/40. 0/60. 0/80. 0GB AT 5-10 T A B G 0 . 0 2 L 6 - X 0 4 7 D r ot x a M 1 1 - 5 UVKHGPG$ GEPCOTQHTG2 noitarepO fo selpicnirP cisaB transferring data requested by the host. Unlike a noncaching controller, Maxtor's disk controller continues a read operation after the requested data has been transferred to the host system. This read operation terminates after a programmed amount of subsequent data has been read into the cache segment. The cache memory consists of a 1. 9MB DRAM buffer allocated to hold the data, which can be directly accessed by the host by means of the READ and WRITE commands. The memory functions as a group of segments with rollover points at the end of cache memory. The unit of data stored is the logical block (that is, a multiple of the 512 byte sector). Therefore, all accesses to the cache memory must be in multiples of the sector size. Almost all non-read/write commands force emptying of the cache: GJEC% GVKT9 When a write command is executed with write caching enabled, the drive stores the data to be written in a DRAM cache buffer, and immediately sends a GOOD STATUS message to the host before the data is actually written to the disk. The host is then free to move on to other tasks, such as preparing data for the next data transfer, without having to wait for the drive to seek to the appropriate track, or rotate to the specified sector. [. . . ] Hard disks most often have sectors that are 512 data bytes long plus several bytes overhead for error correcting codes. Each sector is preceded by ID data known as a Maxtor D740X-6L 20. 0/40. 0/60. 0/80. 0GB AT G-7 Glossary platter is made of beneath the magnetic coating. Hard disks are generally made of aluminum or magnesium alloy (or glass, for optical disks) while the substrate of floppies is usually mylar. SURFACE ­ The top or bottom side of the platter which is coated with the magnetic material for recording data. [. . . ]