On Flash Memory

Image via Wikipedia While one obvious application of flash memory is for the storage of files, it can also act just like ROM memory, where firmware can reside, and also like RAM, to hold temporary information required by the device.

We see flash memory in MP3 players, SD cards (and other memory cards), USB thumb drives and even Solid-State Drives (where NAND flash memory is becoming the standard, replacing RAM-based SSD). Essentially, flash memory is ideal wherever we need cheap, non-volatile multifunction memory and storage, and wherever we would have seen an EEPROM. In fact, flash memory is basically just a type if Electrically Erasable and Programmable/writable memory. At this point, I should mention that there are two types of flash memory - NOR-based, going back the 1980s, and NAND-based, from a few years later. Only NOR-based flash memory is really an ideal replacement for ROM chips, since it allows random access to any memory location. NAND-based flash memory is a bunch of memory cells arranged in series, and read in a block-wise basis which doesn't allow random access to any memory location, making is not particularly suitable to be used as a ROM replacement. However, it is cheaper, and can be fine for simpler devices as not just storage, but ROM too.

Flash memory blurs the distinction between memory and storage. Where storage is somewhere for long term storage of static data, flash memory can be used - so in this way, you might be led to believe that it doesn't belong in the category of memory at all. However, flash memory can be used as a faster alternative to hard-disk based virtual memory - so you can see how in our PCs a portion of their storage can be used for additional memory. Some people use USB thumb drives to replace slow virtual memory with a faster alternative to get a performance boost. MP3 players typically have their firware written either to dedicated NOR flash memory, while some of it is used as memory, or a portion of the NAND flash memory. Usually, NAND-based flash memory is used to store the actual digital media. Cameras can work in much the same way - having on-board flash memory to hold the firmware (as a ROM would) and provide internal storage, as well as the SD, XD or CF memory cards used to store photos. Just think of all the flash memory that goes into smart phones, multiplied by the current and future demand of smart phones, and add to this the demand for the iPad and all the competitors that are starting to appear - then you can get an idea of how prevalent flash memory already is, and how important it will continue to be.

As flash memory becomes faster, I wonder if we'll ever see it replace RAM memory, at least in lower-end consumer devices, just as it has replaced HDD storage and SSD storage is so many applications already.

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