How long is the life of flash memory?

[nvd]

What is the life of flash memory. Are bad sectors possible in this type of memory?

 

[IanP]

Re: Flash memory

According to Toshiba, the inventor of Flash memory: “the 10,000 cycles of MLC NAND is more than sufficient for a wide range of consumer applications, from
storing documents to digital photos. For example, if a 256-MB MLC NAND Flashbased card can typically store 250 pictures from a 4-megapixel camera (a conservative estimate), its 10,000 write/erase cycles, combined with wear-leveling
algorithms in the controller, will enable the user to store and/or view approximately 2.5 million pictures within the expected useful life of the card.” 1 For USB Flash drives, Toshiba calculated that a 10,000 write cycle endurance would enable customers to “completely write and erase the entire contents once per day for 27 years, well beyond the life of the hardware.”
..

Automatic Bad Sector Remapping: .. Flash controllers automatically lock
out sections with bad memory cells (“bad blocks”) and move the data to other
sections (“spare blocks”) to avoid data corruption. During factory formatting (as
described in Section 2), spare blocks are set aside on the Flash storage device for
remapping bad sectors over time.

Quoted from: **broken link removed**

Regards,
IanP

 

[vinay2006]

Re: Flash memory

hi,
Flash memory refers to a particular type of EEPROM, or Electronically Erasable Programmable Read Only Memory. It is a memory chip that maintains stored information without requiring a power source.

Flash memory differs from EEPROM in that EEPROM erases its content one byte at a time. This makes it slow to update. Flash memory can erase its data in entire blocks, making it a preferable technology for applications that require frequent updating of large amounts of data as in the case of a memory stick.

Inside the flash chip, information is stored in cells. A floating gate protects the data written in each cell. Tunneling electrons pass through a low conductive material to change the electronic charge of the gate in "a flash," clearing the cell of its contents so that it can be rewritten. This is how flash memory gets its name.

 

[gigle]

Re: Flash memory

Flash memory utilizes direct tunneling in NAND type flash memory and hot electron in NOR type flash memory. To do this flash memory cells require high voltages. The required voltage level in NAND type is higher than in NOR type because NAND type utilizes direct tunneling. This kind of stress degrade the dielectric quality in flash memory. (Even in just COMS logic gate the switching degrade the dielectric quality) After a number of read/write cycles, when large amount of carriers are trapped in dielectric or some defects grow up, the memory cell can not guarantee the correct data due to the Vt change or leakage, which is the life of flash memory.

In spec, NAND type allow 1 or 2bit error but NOR type doesn't. So NAND type memory uses ECC (error correction code) to recover the bit error.

It is possible to have some bad sectors but they should be controlled by controller (like hard disk).