Phase Change Memory (PCM)‏ ``640K of memory should be enough for anybody.'' -- Bill Gates

Volatile Memory Random Access Memory Static RAM SDRAM Dynamic RAM DRAM Content-addressable memory Cache Controller

Non-Volatile Memory Read Only Memory Flash Memory Magnetic Storage  Hard Disks  Floppy Disks  Magnetic Tape Optical Storage Dead tree (punch cards)‏ And....

Phase Change Memory ”PRAM uses the unique behavior of chalcogenide glass, which can be "switched" between two states, crystalline and amorphous, with the application of heat. Recent versions can achieve two additional distinct states, effectively doubling its storage capacity.” --Wikiepedia link

History Originaly reearched in the 1960's Gordon Moore of Intel wrote a research paper about the benefits and memory implications of chalcogenide glasses

Physical Properties Diferent states have different qualities  Amorphorous State High resistivity represents 0  Crystaline State Low resistivity represents  Different states have different optical properties Used in re writable cds/dvds

Flash vs Pram Flash  Changeing Bits must be across blocks  Requires a time to build up a charge (1 ms)‏  Degrades with use (10,000 to 100,000 writes)‏ Pram  Individual bits can be changed  Low power consumption  Degrades slowly (100 million)‏  At 85 C data can last 300 years

PRAM today 2004 Samsung Prototyped a 512 MB module 2006 Intel created a mass producible 128 module 2008 Inte discovered 2 addition states effectively doubling the Capacity 2008 Intel begins shipping beta version called Alverstone

Phase Change Memory (PCM)‏ Grant Callaghan Sources  Wikipedia  Murdocca,Miles Computer Architecture and Organization, 2007 John Wiley and Sons  San Jose State Professor Sin Min Lees cs147 slides