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Spinpoint M8U-Internal Product Manual REV 3.4
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INSTALLATION
The ENDEC of 88C9310 decodes the 30/32 with post-processor format to produce a serial bit stream. This
NRZ (Non Return to Zero) serial data is converted to 12-bit bytes.
The Sequencer module identifies the data as belonging to the target sector. After a full sector is read, the
88i9322 (Rev2.0) checks to see if the firmware needs to apply an ECC algorithm to the data.
The Buffer Control section of the 88i9322 (Rev2.0) stores the data in the cache and transmits the data to the
AT bus.
5.4.2 The Write Channel
The signal path for the Write Channel follows the reverse order of that for the Read Channel. The host
transmits data via the AT bus to the 88i9322 (Rev2.0) Interface Controller. The Buffer Controller section of
the 88i9322 (Rev2.0) stores the data in the cache. Because the data is transmitted to the drive at a rate that
exceeds the rate at which the drive can write data to the disk, data is stored temporarily in the cache. Thus,
the host can present data to the drive at a rate independent of the rate at which the drive can write data to the
disk.
Upon correct identification of the target address, the data is shifted to the Sequencer, which generates and
appends an error correcting code. The Sequencer then converts the bytes of data to a serial bit stream. The
AT controller also generates a preamble field, inserts an address mark, and transmits the data to the ENDEC
in the R/W IC where the data is encoded into iterative code format and pre-compensates for non-linear
transition shift. The amount of write current is set by the 88i9322(Rev2.0) DSP and Interface/Disk
Controller through the serial interface to the preamplifier.
The 88i9322 (Rev2.0) switches the Preamplifier and Write Driver IC to write mode and selects a head. Once
the Preamplifier and Write Driver IC receives a write gate signal, it transmits current reversals to the head,
which writes magnetic transitions on the disk
5.5 Firmware Features
This section describes the following firmware features:
• Read Caching
• Write Caching
• Track Skewing
• Defect Management
• Automatic Defect Allocation
• ECC Correction
5.5.1 Read Caching
The Spinpoint M8U hard disk drive uses an 8MB Read Cache to enhance drive performance and
significantly improve 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 utilizes 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 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 time savings during at least half of all disk requests. For