by Thomas Coughlin

• Common flash memory cards
• The most common flash memory products currently in use are SD cards and derivative products (e.g. mini and micro-SD cards)
• Some compact flash used for professional applications (such as DSLR cameras)
• Evolution of leading flash formats
• Standardization –> market expansion
• Market expansion –> volume
• iNAND –> focus is on enabling embedded X3
• iSSD –> ideal for thin form factor devices
• Flash memory applications
• Phones are the #1 user of flash memory
• Flash memory is used as embedded and removable storage in many mobile applications
• Flash memory is being used in computers as USB sticks and SSDs
• Possible use of flash memory in computer combined with HDDs (hybrid HDDs and paired or dual storage computers)
• It can be a removable card or an embedded card
• These devices can only handle a specific number of writes
• Flash memory reads considerably quicker than hard drives
• Hybrid and dual storage in computers
• SSDs can provide fast performance but they are expensive
• HDDs can provide cheap storage but they are relatively slow
• Combining some flash memory with a HDD can provide costs close to those of HDDs and performance close to flash memory
• Seagate Momentus XT hybrid HDD
• Various dual storage offerings putting flash memory with HDDs
• Other common flash memory devices
• USB sticks
• All forms and colors
• Used for moving files around
• Some sold with content on them (Sony Movies on USB sticks)
• Solid State Drives (SSDs)
• Floating Gate Flash Memory Cell
• When a bit is programmed, electrons are stored upon the floating gate
• This has the effect of offsetting the charge on the control gate of the transistor
• If there is no charge upon the floating gate, then the control gate’s charge determines whether or not a current flows through the channel
• A strong charge on the control gate assumes that no current flows. A weak charge will allow a strong current to flow through.
• Similar to HDDs, flash memory must provide:
• Bit error correction
• Bad block management
• NAND and NOR memories are treated differently when it comes to managing wear
• In many NOR-based systems no management is used at all, since the NOR is simply used to store code, and data is stored in other devices. In this case, it would take a near-infinite amount of time for wear to become an issue since the only time the chip would see an erase/write cycle is when the code in the system is being upgraded, which rarely if ever happens over the life of a typical system.
• NAND is usually found in very different application than is NOR
• Flash memory wears out
• This is expected to get worse over time
• Retention: Disappearing data
• Bits fade away
• Retention decreases with increasing read/writes
• Bits may change when adjacent bits are read
• Time and traffic are concerns
• Controllers typically groom read disturb errors
• Like DRAM refresh
• Increases erase/write frequency
• Application characteristics
• Music – reads high / writes very low
• Video – r high / writes very low
• Internet Cache – r high / writes low
• On airplanes
• Many consumers now have their own content viewing devices – do they need the airlines?
• Is there a way to offer more to consumers, especially with their own viewers
• Additional special content
• tie into airplane network
• access to electrical power, internet
• Should there be fixed embedded or removable storage for on-board airline entertainment?
• Is there a way to leverage personal and airline viewers and content in new and entertaining ways?