The Rise to Dominance of NAND Flash

Flash memory is the dominant form of non-volatile memory for embedded systems and has been since the EEPROM days. I remember using an ultraviolet lamp to erase the old EPROMs, those were the days. You could erase your EPROM and permanently damage your eyesight at the same time!

NOR flash, traditionally dominant in embedded systems, has provided as a relatively small amount of non-volatile memory for booting the device and retaining critical parameters during power-off. NOR flash was a good choice because it supports execute-in-place which removes the need to copy the entire image from flash to RAM to execute. Given the relatively small amount of storage needed in the past, NOR remained the dominant technology.

In the past few years the demand for NAND flash has increased significantly. According to Gartner the market has grown from $7 billion to $15 billion since 2004. The significant contribution to this growth is USB flash drives and digital music players. In fact, Apple alone can cause shortages in the NAND flash marketplace with devices like the iPhone and iPods. Why has NAND taken off as the dominant technology? One of the reasons is the difference in silicon-level geometry. NAND flash gates are about 60% smaller than the equivalent NOR gate. This allows more gates per die and therefore higher density and more storage capacity.

NAND and NOR geometry compared (image from Micron)
There are also other advantages to NAND flash in that it behaves more like a hard disk since the storage media is sector-based making it ideal for sequential data (mp3s, pictures, video). NAND flash also has very fast write and erase performance. NOR and NAND flash have similar sustained read speeds although NOR has the advantage in random access. However, its structural advantage is arising in much greater densities and better overall performance, NAND has become the technology leader in flash. Consequently, as the demand for higher capacity continued, NAND has become the market revenue leader as well.

Datalight FlashFX Pro
Embedded operating systems need to support flash file systems since many embedded systems use flash nowadays. Flash is treated like a block file system in the OS but requires specialized software at the lower driver level. In our case we rely on our partner, Datalight, with their FlashFX Pro software to provide this interface. The beauty of this solution is that the OS can treat the flash media as a regular block-based disk and the FlashFX Pro software deals with the complexity of the underlying media.

Why is there the need for a media interface like this? NAND is more complex to deal with than hard disk. For example, there is limited number of writes that a NAND device can support. Wear levelling and bad block management is critical to device reliability and longevity, however, it needs to be done properly and efficiently. Why FlashFX Pro? Datalight is the flash memory media management expert r and provides support for 100's of different brands of flash. The company’s proven solution provides high performance, reliability and broad hardware support – all key things for embedded devices.

Our recent reseller announcement with Datalight is great timing because flash memory file systems are table-stakes for embedded systems. We can now offer FlashFX Pro directly to our customers.

3 Comments

  1. Kerri McConnell

    Thanks for highlighting the importance of NAND flash in the embedded ecosystem. As embedded systems store more and more data, the capacity that NAND can provide cost-effectively makes it a great fit. Datalight is pleased to provide state-of-the-art flash management for VxWorks. There are several whitepapers on this topic in our website.

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