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Momentus XT Product Manual, Rev. A 5
2.2 Formatted capacity
Model Formatted capacity* Guaranteed sectors Bytes per sector
ST95005620AS 500GB 976,773,168 512
ST93205620AS 320GB 625,142,448 512
ST92505610AS 250GB 488,397,168 512
*One GB equals one billion bytes when referring to hard drive capacity. Accessible capacity may vary depending on operating environment
and formatting.
2.2.1 LBA mode
When addressing these drives in LBA mode, all blocks (
sectors) are consecutively numbered from 0 to n–1,
where n is the number of guaranteed sectors as defined above.
See Section 4.3.1, "Identify Device command" (words 60-61 and 100-103) for additional information about 48-
bit addressing support of drives with capacities over 137GB.
2.2.2 Solid State Hybrid feature
The Solid State Hybrid feature utilizes the addition of NAND Flash mem
ory to enhance the performance of the
drive. Short random accesses to the NAND Flash are faster than disc accesses due to the elimination of seek
and rotational latencies and therefore it is used to store more frequently accessed data. The Momentus XT
uses a proprietary algorithm which monitors drive activity and determines the optimum data to maintain in the
NAND Flash for peak responsiveness. The Solid State Hybrid feature is self contained in the drive firmware
and functions independent of the host hardware or operating system. There are no special host system
requirements. Momentus XT can be installed in any standard SATA environment and will automatically opti-
mize.
Specifics of the Solid State Hybrid Feature:
• Powerful ECC correction on data read from the NAND Flash.
• Maintains a list of defective NAND Flash blocks and maps them out of use.
• Additional bad blocks added during
use will be added to the list of defective blocks and taken out of use.
• Storage functionality is preserved with no dat
a loss with any wear out of the NAND Flash.
• No user intervention required.
2.3 Default logical geometry
Cylinders Read/write heads Sectors per track
16,383 16 63
LBA mode
When addressing these drives in LBA mode, all blocks (sectors) are consecutively numbered from 0 to n–1,
where n is the number of guaranteed sectors as defined above.