IBM announces computer memory breakthrough

Phase-change memory offers 100 times the write performance of NAND flash

 IBM Thursday announced a breakthrough in computer memory technology, which may lead to the development of solid-state chips that can store as much data as NAND flash technology but with 100 times the performance and vastly greater lifespan.

Currently, NAND flash memory products, such as SSDs, have write rates as high as 2Gbit/sec.

IBM said it has produced phase-change memory (PCM) chips that can store two bits of data per cell without data corruption problems, something that has plagued PCM development from the start.

IBM's phase-change memory chip uses circuitry that is 90 nanometers in width

Like NAND flash memory, which is used in solid state drives (SSDs) and is embedded in computers like Apple's MacBook Air, PCM is nonvolatile -- meaning it retains data after its power supply is shut down.

Unlike NAND flash, PCM memory does not require that existing data be marked for deletion prior to new data being written to it -- a process known to as an erase-write cycle. Erase-write cycles slow NAND flash performance and, over time, wear it out, giving it a lifespan that ranges from 5,000 to 10,000 write cycles in consumer products and up to 100,000 cycles in enterprise-class products.

PCM can sustain up to 5 million write cycles, according to IBM.

"If you can write to flash 3,000 times, that will outlive most cell phones and MP3 players, but that's certainly not good enough for the enterprise that does that in an hour," said Christopher Sciacca, manager of communications for IBM Research in Zurich.

As organizations and consumers increasingly embrace cloud-computing models and services, ever more powerful and efficient, yet affordable storage technologies are needed, according to Haris Pozidis, manager of memory and probe technologies at IBM Research.

Pozidis said that for the past five months, teams of IBM scientists have been testing a multi-level cell (MLC) chip that's capable of storing two and eventually three bits of data, indicating that it can achieve a level of reliability that is suitable for practical applications.

Besides applications for enterprises and in the cloud, PCM may also serve as an extension for DRAM.

While DRAM will continue to be used as the closest memory device to the CPU for the most active data, Pozidis said, PCM, with its greater capacity, can be used for less frequently accessed data. "The PCM, which is much larger, acts as a repositor. If the data becomes hot again it will move back to the DRAM," he said.

In another scenario, Pozidis said, the CPU can talk directly to the PCM, but it thinks its talking to the DRAM using a controller. "Again, the hot data speaks to DRAM and not so hot data speaks to the PCM," he said.