M.2 2242 Flash Drive
APM2T42P100xxxxAN-XTX
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© 2015 Apacer Technology Inc. Rev. 1.2
4. Flash Management
4.1 Error Correction/Detection
P100 implements a hardware ECC scheme, based on the BCH algorithm. It can detect and correct up to
72 bits error in 1K bytes.
4.2 Bad Block Management
Bad blocks are blocks that include one or more invalid bits, and their reliability is not guaranteed. Blocks
that are identified and marked as bad by the manufacturer are referred to as “Initial Bad Blocks”. Bad
blocks that are developed during the lifespan of the flash are named “Later Bad Blocks”. Apacer
implements an efficient bad block management algorithm to detect the factory-produced bad blocks and
manages any bad blocks that appear with use. This practice further prevents data being stored into bad
blocks and improves the data reliability.
4.3 Wear Leveling
NAND flash devices can only undergo a limited number of program/erase cycles, and in most cases, the
flash media are not used evenly. If some areas get updated more frequently than others, the lifetime of
the device would be reduced significantly. Thus, Wear Leveling is applied to extend the lifespan of NAND
flash by evenly distributing write and erase cycles across the media.
Apacer provides advanced Wear Leveling algorithm, which can efficiently spread out the flash usage
through the whole flash media area. Moreover, by implementing both dynamic and static Wear Leveling
algorithms, the life expectancy of the NAND flash is greatly improved.
4.4 Power Failure Management
Power Failure Management plays a crucial role when experiencing unstable power supply. Power
disruption may occur when users are storing data into the SSD. In this urgent situation, the controller
would run multiple write-to-flash cycles to store the metadata for later block rebuilding. This urgent
operation requires about several milliseconds to get it done. At the next power up, the firmware will
perform a status tracking to retrieve the mapping table and resume previously programmed NAND blocks
to check if there is any incompleteness of transmission.
4.5 ATA Secure Erase
ATA Secure Erase is a standard ATA command and will write all “0xFF” to fully wipe all the data on hard
drives and SSDs. When this command is issued, the SSD controller will empty its storage blocks and
return to its factory default settings.
4.6 TRIM
TRIM is a feature which helps improve the read/write performance and speed of solid-state drives (SSD).
Unlike hard disk drives (HDD), SSDs are not able to overwrite existing data, so the available space
gradually becomes smaller with each use. With the TRIM command, the operating system can inform the
