Ecc

Valuable Memory Technical Resources

India Inst of Tech Hyderabad SealEver since moving to Silicon Valley some time ago The Memory Guy has worked with a number of impressively-talented engineers from India.  Some are educated in the US, while others are educated in India.  One university that produces excellent engineers is the Indian Institute of Technology, or IIT.

It comes as no surprise, then, to find a valuable resource produced by an IIT faculty member.  Dr. Sparsh Mittal, an assistant professor at IIT Hyderabad, reached out to me to share some papers that he thought might be of interest to Memory Guy readers. They were a few of roughly 40 papers that he has posted on his publications page.  He explained that he previously worked at Oak Ridge National Lab, in the US.

Dr. Sparsh has published several very comprehensive surveys on memory systems, both conventional and emerging, covering topics like DRAM reliability, NVM/Flash, ReRAM-based processing-in-memory, and the architecture of neural networks.  The web page lists 34 surveys, eight of them Continue reading

How 3D NAND Shrinks ECC Requirements

Bit Errors vs. ProcessError Correction Codes, ECC, are not only important to today’s NAND flash market, but they have been a cause of concern to NAND users for a number of years.  The Memory Guy has been intending for some time to write a low-level primer on ECC, and I am finally getting it done!

Why is ECC necessary on NAND flash, yet it’s not used for other memory technologies?  The simple answer is that NAND’s purpose is to be the absolute cheapest memory on the market, and one way to achieve the lowest-possible cost is to relax the standards for data integrity — to allow bit errors every so often.  This technique has been used for a long time in both communications channels and in hard disk drives.  Data communication systems can transfer more data using less bandwidth and a weaker signal over longer distances if they use error correction to restore distorted data.  Hard disk drives can pack more bits onto a platter if the bits don’t all have to work right.  These markets (and probably certain others) have invested a lot of money in ECC research and development, and as a result ECC today  is a very well-developed science.

Denali Software published a nice Continue reading