Disk Drive Operation
WA31273A / WA32543A / WA33203A / WA32163A / WA31083A / WA32162A5-15
5-5
Firmware Features
This section describes the firmware features as follows:
•
Read Cache
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Write Cache
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Write Auto Reassign
•
Defect Management
•
Power Management
•
Triple burst ECC Correction
•
SMART (Self-monitoring and reporting technology)
5-5-1
Read Caching
The Winner 3A WA31273A / WA32543A / WA33203A / WA32163A / WA31083A, Winner 2A
WA32162A hard disk drives use a 128K Read Cache to enhance drive performance. The feature
significantly improves system throughput. Use the SET FEATURES command to enable or disable
Read Caching. Read caching anticipates host-system requests for data and stores that data for faster
future access. When the host requests a certain segment of data, the cache feature uses a prefetch
strategy to get the data in advance and automatically read and store the following data from the disk
into fast RAM. If the host requests this following data, the RAM is accessed rather than the disk.
There is a high probability that subsequent data requested will be in the cache, because more than 50
percent of all disk requests are sequential. It takes microseconds rather than milliseconds to retrieve
this cached data. Thus Read Caching can provide substantial performance improvements during at
least half of all disk requests. For example, Read Caching could save most of the disk transaction time
by eliminating the seek and rotational latency delays that prominently dominate the typical disk
transaction.
Read Caching operates by continuing to fill its cache memory with adjacent data after transferring data
requested by the host. Unlike a non-caching controller, the SID-9501D interface Controller block
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
memory.
The cache memory consists of a 128K SRAM buffer allocated to hold the data. This cache memory
can be directly accessed by the host by means of read and write commands. The unit of data stored is
the logical block, or a multiple of the 512-byte sector. Therefore, all accesses to cache memory must
be in multiples of the sector size. The following commands empty the cache:
•
IDENTIFY DRIVE (ECh)
•
FORMAT TRACK (50h)
