Category: wintel

The big question is endurance, however we wont see a reduction in write cycles this time around. IMFTs 20nm client-grade compute NAND used in consumer SSDs is designed for 3K – 5K write cycles, identical to its 25nm process.

via AnandTech – Intel and Micron IMFT Announce Worlds First 128Gb 20nm MLC NAND.

If true this will help considerably in driving down cost of Flash memory chips while maintaining the current level of wear and performance drop seen over the lifetime of a chip. Stories I have read previously indicated that Flash memory might not continue to evolve using the current generation of silicon chip manufacturing technology. Performance drops occur as memory cells wear out. Memory cells were wearing out faster and faster as the wires and transistors got smaller and narrower on the Flash memory chip.

The reason for this is memory cells have to be erased in order to free them up and writing and erasing take a toll on the memory cell each time one of these operations is performed. Single Level memory cells are the most robust, and can go through many thousands even millions of write and erase cycles before they wear out. However the cost per megabyte of Single Level memory cells make it an Enterprise level premium price level for Corporate customers generally speaking. Two Level memory cells are much more cost effective, but the structure of the cells makes them less durable than Single Level cells. And as the wires connecting them get thinner and narrower, the amount of write and erase cycles they can endure without failing drops significantly. Enterprise customers in the past would not purchase products specifically because of this limitation of the Two level memory cell.

As companies like Intel and Samsung tried to make Flash memory chips smaller and less expensive to manufacture, the durability of the chips became less and less. The question everyone asked is there a point of diminishing return where smaller design rules, thinner wires is going to make chips so fragile? The solution for most manufacturers is to add spare memory cells, “over-providing” so that when a cell fails, you can unlock a spare and continue using the whole chip. The over -provisioning no so secret trick has been the way most Solid State Disks (SSDs) have handled the write/erase problem for Two Level memory cells. But even then, the question is how much do you over-provision? Another technique used is called wear-levelling where a memory controller distributes writes/erases over ALL the chips available to it. A statistical scheme is used to make sure each and every chip suffers equally and gets the same number of wear and tear apllied to it. It’s difficult balancing act manufacturers of Flash Memory and storage product manufacturers who consume those chips to make products that perform adequately, do not fail unexpectedly and do not cost too much for laptop and desktop manufacturers to offer to their customers.

If Intel and Micron can successfully address the fragility of Flash chips as the wiring and design rules get smaller and smaller, we will start to see larger memories included in more mobile devices. I predict you will see iPhones and Samsung Android smartphones with upwards of 128GBytes of Flash memory storage. Similarly, tablets and ultra-mobile laptops will also start to have larger and larger SSDs available. Costs should stay about where they are now in comparison to current shipping products. We’ll just have more products to choose from, say like 1TByte SSDs instead of the more typical high end 512GByte SSDs we see today. Prices might also come down, but that’s bound to take a little longer until all the other Flash memory manufacturers catch up.

Related articles

• IMTF exposes its incredible shrinking NAND (go.theregister.com)