In computer architecture, a term ‘Non-Volatile Memory’ (NVM) is referring to a type of memory that doesn’t require any moving parts to perform the read or write operations, nor it needs to refresh its content periodically in order to keep it stored. That basically means that a NVM is the type of computer memory that can preserve the stored information even when the power is turned off. NVM’s are thus used mainly to persist the information. The category of non-volatile memory types “includes all forms of read-only memory (ROM) such as programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory.” (Posted and Rouse, 2005).
As of 2016, mass produced are mainly the following types of non-volatile memories: NOR Flash, NAND Flash, MRAM, and FeRAM.
The NOR Flash and NAND Flash memory types are very similar. The NOR is often used in the mobile devices such as smartphones, as it’s significantly faster than NAND. On the other hand, NAND technology is less expensive and also allows for more data storage, so we see it being used in SSD drives. Sometimes we can see the both types being implemented side by side in a single device, where NOR stores the operating system, while NAND functions as general storage. The only significant difference between NOR and NAND is in the way they connect individual memory cells. NOR supports one bite random-access reading and writing operation, because it has the memory cells connected in parallel to bit lines. This is different from NAND which can only access the data serially (page access), due to memory cells connected in series. It’s important to note that both types offer certain advantages. The reason we see a dramatic emergence of the NAND memory type is the reduced cost per bit “and increased maximum chip capacity so that flash memory can compete with magnetic storage devices like hard disks.” (WhatIs, 2013). Due to these advantages, the NAND entrance to market was boosted by recent sales of smartphones. According to IC Insights, the sales of smartphones accounted for about “26 percent of total NAND sales in 2013” (Hajdarbegovic, 2013).
In the market that has been dominated by NAND and NOR for close to 30 years, MRAM memory types is yet another type of memory that is being mass produced. IBM, Hynix & Fujitsu are among the market leaders, but the sale volumes are low. The sales of MRAM only account for a minuscule chunk (< $300 million in 2012) of the worldwide flash memory sales (26 billion in 2012). The proponents of MRAM believe that the advantages “are so overwhelming that magnetoresistive RAM will eventually become dominant for all types of memory” (Magnetoresistive, 2016). But considering that MRAM was proposed almost 25 years ago, chances of this statement being correct appear to be low side. In my opinion, MRAM can be reincarnated in a newer technology, that has a higher chance of uptake. That technology is called the Spin-Transfer Torque (STT) MRAM or just: STT MRAM. STT-MRAM similarly to NOR or NAND also retains the data indefinitely – even when the power is completely turned off. We can already see this type of memory entering the early production markets, and since it is non-volatile, “STT MRAM, is well suited for many mainstream applications, especially since a storage technology, delivering the high performance of DRAM and SRAM, and the low power and low cost of flash memory.” (U.A.R., 2016). It is projected that “STT-RAM revenues are expected to increase from about $300 M in 2014 to between $1.35 B and $3.15 B by 2020 with a medium projection of $1.35 B.” (Coughlin, 2015)
The last type of non-volatile memory types that I want to mention is the one that has only recently entered the industrial production, called FeRAM. FeRAM is using the ferroelectric layer to achieve non-volatility. The main advantage of this technology is also that FeRAM memory is very scalable. We should soon be able to see the first 16 MB chips available, “but we do not expect it to be widely industrialized and commercialized before 2018.” (Meena, J.S., Sze, S.M., Chand, U. and Tseng, T.-Y. , 2014)
What does the future hold for us?
Let’s talk about the future. One of the emerging NVM technologies that is gaining a lot of attention nowadays is the 3-D ReRAM. This technology hints at the future to come. The 3-D RRAM works by changing the resistance across a dielectric material, and it is expected to hit the market in 2017. The major industry players hope to see a massive RRAM ramp-up in the years to come. A good signal of this trend was an announcement made during the Flash Memory Summit in Santa Clara, California (on Tuesday, August 16, 2016). The Western Digital said that they “intend to use 3D ReRAM as storage class memory for its future ultra-fast SSDs.” (Western Digital to get into 3D ReRAM, 2016).
Some of us still remember early 2005, when Toshiba and SanDisk developed a 1GB NAND flash chip. And it didn’t take that long and Samsung introduced us to 2 GB chip which was in September 2006 replaced by 8 GB capacity and 40 nm manufacturing process. And just two years later, in 2008 the 32 GB chip entered the market, followed by 256 GB cards in 2012. Now we’re writing down the year 2016, and 1TB SSD flash drives are priced below the US $300 and will soon become a common type of NVM used in our devices.
So what’s next? Well, start thinking about 10 TB SSD drives, because only recently, a joint development at Intel and Micron announced that they will be able to initiate the production of “32 layer 3.5 terabyte (TB) NAND flash sticks” (Flash memory, 2016). Intel says, “this will create 1TB SSDs that will fit in mobile form factors and 10TB enterprise-class SSDs, by 2018.” (Goodwins, 2015)
Earlier on, I’ve mentioned the 2016 Flash Memory Summit. One of the keynote talks that took place on 16th of August 2016, provided couple more clues into what awaits us in the future. E.g. Samsung and Seagate mentioned that 100 TB SSDs will be available by 2020 and that we will also see 64GB chips that use data transfer rates at 800 Mbps. Samsung also introduced a “3 bit per cell 1 TB ball-grid array (BGA) SSD, weighing about 1 gram, aimed at compact laptops, tablet, and other mobile devices. This device has sequential read speeds of 1,500 MBps and write speeds of 900 MBps.” (Coughlin, 2016).
That’s said, let’s transport ourselves into 2020 and imagine a smartphone that houses an earlier mentioned 100 TB SSD storage. How much can we fit on a smartphone that has 100 TB of free space? Hold your seat, what I am about to tell you is truly incredible. 100 TB drive can save 1.7 million hours or audio, 31 million hi-resolution photos, or the amount of video that would continuously play for over ten years. Or how about fitting entire English Wikipedia onto this device? As of May 2016, the entire English Wikipedia had a total download size of 53 GB (compressed readable version), which means it would fit more than 1,800 times on such a high capacity drive.
So, these are the trends we’re approaching. Ability to hold years worth of music and movies and entire copies of encyclopedia’s – all in our pocket.
Another future trend we may see is using non-volatile memories in place of volatile memory types. These ideas are already changing computer concepts. A good example of the practice is replacing the volatile memory with a non-volatile type as a means to store computer’s BIOS. When we boot up a computer, it must firsts load the BIOS, whose goal is to keep all the computer instructions, settings and configurations intact even when we lose the power. In modern computer systems, the BIOS contents are stored on a flash memory chips, which are non-volatile. However, some of us can still recall motherboards that were using volatile memories and had to have a small separate battery placed on the motherboard to power the BIOS and protect the changes we’ve made to our firmware settings.
The computer as we know it, always consisted of a fast & volatile memory typically placed directly on the motherboard, and a slow & non-volatile memory that stored the data and could be connected to a computer using a wire, USB cable, etc. What future trends will we see if NVRAM types starts to replace volatile memories? In my opinion, the idea of volatile memories replaced by large, fast, non-volatile memory systems, would change everything. I am imagining a future system that has no disk and memory paging (one level of non-volatile storage wouldn’t need to page), no buffer cache, no page faults, no swapping and no booting on restart. This would change the present design of the operating systems, but also a number of other OS mechanisms, functions, and properties.
Note: If you want to access BIOS on your computer, simply power your computer on, and as soon as the first logo screen appears, immediately start pressing the F2 (laptop) or the DEL key on a desktop. You can explore the settings, just be careful not to change anything as any of the changes could have a negative impact on the settings.
What sort of impact will this have on our society?
For one, I believe it’ll be a positive experience. Most of us need to be connected to the Internet to access the static information. And Internet is slow, impacted by the bandwidth or actual speed of the connection in given geo location. If we could store most of the information we’re accessing on a non-volatile medium, and keep it always available in an offline mode, our access to information would dramatically speed up. It would only be limited by the speed of retrieval from the NVM memory.
This type of storage capacities could also come with a significant economic benefits. Perhaps one day, 50 years from now, we won’t be buying the empty NVM memories, but preconfigured NVM storage cards that can hold entire libraries of movies and music.
How about a copy of all movies along with an offline copy of IMDB’s web site? Or how about an offline copy of the entire internet? You may be saying that that is surely impossible? Perhaps, but let’s not forget, that it was only 11 years ago in 2005 that Toshiba’s 1GB card entered the market and in the single decade since, we’ve figured out how to produce 100 TB storage or a 1 TB that weighs only 1 gram.
Coughlin, T. (2015) Emerging non-volatile memory technology drives equipment sales. Available at: http://www.forbes.com/sites/tomcoughlin/2015/11/12/emerging-non-volatile-memory-technology-drives-equipment-sales/#17fa34147378 (Accessed: 19 August 2016).
Posted and Rouse, M. (2005) What is nonvolatile memory? – definition from WhatIs.com. Available at: http://searchstorage.techtarget.com/definition/nonvolatile-memory (Accessed: 19 August 2016).
Flash memory (2016) in Wikipedia. Available at: https://en.wikipedia.org/wiki/Flash_memory#Capacity (Accessed: 19 August 2016).
Goodwins, R. (2015) The future of storage: 2015 and beyond. Available at: http://www.zdnet.com/article/the-future-of-storage-2015-and-beyond/ (Accessed: 19 August 2016).
Coughlin, T. (2016) Flash memory summit keynotes outline the future of solid state storage. Available at: http://www.forbes.com/sites/tomcoughlin/2016/08/18/flash-memory-summit-keynotes-outline-the-future-of-solid-state-storage (Accessed: 19 August 2016).
WhatIs (2013) What is NAND flash memory ?. Available at: http://whatis.techtarget.com/definition/NAND-flash-memory (Accessed: 19 August 2016).
Meena, J.S., Sze, S.M., Chand, U. and Tseng, T.-Y. (2014) ‘Overview of emerging nonvolatile memory technologies’, 9(1).
Hajdarbegovic, N. and TGDaily (2013) NAND memory market rockets. Available at: http://www.tgdaily.com/hardware-brief/71015-nand-memory-market-rockets (Accessed: 19 August 2016).
Magnetoresistive random-access memory (2016) in Wikipedia. Available at: https://en.wikipedia.org/wiki/Magnetoresistive_random-access_memory (Accessed: 19 August 2016).
Reserved, U.A.R. (2016) What is STT-MRAM?. Available at: http://www.eetimes.com/author.asp?doc_id=1323466 (Accessed: 19 August 2016).
Western digital to get into 3D ReRAM (2016) Available at: http://www.simmtester.com/page/news/shownews.asp?num=18402 (Accessed: 19 August 2016).
Foo, M. (2012) How much can a 1 TB hard drive hold?. Available at: http://www.pcninja.us/how-much-can-a-1-tb-hard-drive-hold/ (Accessed: 19 August 2016).
Enwiki dump progress on 20160801 (2016) Available at: https://dumps.wikimedia.org/enwiki/20160801/ (Accessed: 19 August 2016).
Bailey, K., Ceze, L., Gribble, S.D. and Levy, H.M. (no date) Operating system implications of fast, cheap, non-volatile memory. Available at: http://sampa.cs.washington.edu/papers/bailey-hotos11.pdf (Accessed: 20 August 2016).
BIOS (2016) in Wikipedia. Available at: https://en.wikipedia.org/wiki/BIOS (Accessed: 20 August 2016).
5, Nsdc. (2012) How to clear your computer’s CMOS to reset BIOS settings. Available at: http://www.howtogeek.com/131623/how-to-clear-your-computers-cmos-to-reset-bios-settings/ (Accessed: 20 August 2016).
Paging (2016) in Wikipedia. Available at: https://en.wikipedia.org/wiki/Paging (Accessed: 20 August 2016).
The buffer cache (no date) Available at: http://www.tldp.org/LDP/sag/html/buffer-cache.html (Accessed: 20 August 2016).