NVDIMM will be an important component of the PC in the near future. This absurdly fast memory type combines the best of RAM and hard drives on a single board
A few years ago, the hard disk was the biggest bottleneck in PCs and notebooks. Their slow data access operations (in double-digit milliseconds) slowed the system – The CPU, RAM and graphics card took a break, and the user was left to wait for a heavy application like Photoshop or a game to be loaded.
This changed with the advent of SSDs, which have now become a standard feature for the system drive. Nowadays, the Flash hard drives aren’t just available for the SATA port, which restricts them due to its maximum transfer rate of 600 MBytes/s. The latest-generation SSDs are connected via the same connector type as the graphics card, and they transfer their data via NVMexpress (NVMe) at a speed of more than 2 GByte/s.
Pretty soon, that too will be a thing of the past, because with NVDIMM, the market will soon see a memory type that is as fast as RAM, and which is set to turn the fundamental concept of the PC inside out.
The idea is evident in the name itself: ‘NV’ stands for ‘non-volatile’, i.e. a storage medium that retains its data contents when the power supply is switched off. ‘DIMM’ stands for ‘dual inline memory module’, which is the technical term for a RAM module. Thus, NVDIMM combines the hard drive and the RAM. In the future, when you start up an NVDIMM PC, it will only have to initiate the hardware, and everything will be at the ready: The operating system, applications, games, documents and files will remain in the RAM, and will not have to be loaded.
At the push of a button, you will be able to continue working from where you left off. The PC – if one still chooses to call it that – will become quite compact, since it will essentially only consist of a CPU and an NVDIMM. In a few years, enthusiast gamers will be the only ones who will need an additional graphics card.
A Standard For Turbo Module
JEDEC (Joint Electron Device Engineering Council) has announced that a separate standard for NVDIMMs will be unveiled in 2015. According to the new standard, the new memories should be compatible with each DDR4-RAM port, and register themselves as such within the system. This means that NVDIMM will be compatible with every hardware platform that uses DDR4-RAM. This includes Skylake, Intel’s newest CPU generation for the PC. However, the new NVDIMMs are very likely to rely on the LRDIMM structure type, where ‘LR’ stands for ‘load reduced’. The difference between this arrangement and the conventional RAM in the home PC is that an LRDIMM features additional buffer memories, which make it possible to process several parallel storage and reading procedures in a more efficient manner.
These buffer memories facilitate higher clock frequencies and larger capacities per RAM module. LRDIMMs are not supported by PC motherboards – Except for the workstation variants for the expensive Haswell-E high-end CPU. Consequently, NVDIMMs such as Diablo Memory 1 will initially be released for special server applications, not for PCs.
The standard defines the NVDIMM-N and NVDIMM-F variants. A memory module belonging to the NVDIMM-N type accommodates RAM chips as well as SSD chips. The SSD chips serve as an integrated backup medium for the RAM data, which would otherwise be lost in case of power failures or damage to the hardware. While NVDIMM-N simply expands the concept of the RAM, NVDIMM-F is designated as a hard disk within the system. NVDIMM-F contains no RAM cells, just Flash chips. Both variants optimise high-performance computing, which refers to the acceleration of computing operations involving large data sets, such as weather simulation or high-frequency trading. However, a few more steps will have to be taken before NVDIMM can be made usable in future PCs.
A Potential Successor To Flash?
If the hard disk and the RAM are going to blend with each other, the storage methods have to be work together. RAM cells can be filled up with data very quickly, and the value of each cell can be changed individually. However, the storage density is not particularly high: A DDR4 module can currently accommodate a maximum of 64 GB. The process of re-writing a Flash cell takes quite a long time, since this is only accomplished in a block-by-block manner. One block encompasses several KB, and thousands of Flash cells. Unlike RAM, relatively high voltages are required for filling up the Flash cells, which is why this memory type can only withstand a limited number of deletion/writing cycles. The major advantage of Flash lies in its high storage density: The latest flash storage technology allows you to set up a terabyte-SSD as an NVDIMM.
For more than a decade, researchers have been puzzling over a storage method that would combine the advantages of RAM and Flash. Sector experts see potential in three different candidates: Phase Change Memory, Resistive RAM and Spin-transfer Torque. All three come close to the performance of RAM, and store data like a hard disk. So far, there have only been prototypes and small-scale series, which were not suitable to be introduced into the market. That changed over the summer, when Intel and Micron announced that the joint-developed 3D XPoint memory type would be released in 2016. 3D XPoint will use one of the three successors, but it’s not yet clear which one it’s going to be. However, Intel did announce that 3D XPoint would be available as an NVMe SSD, and as an NVDIMM. Thanks to this, next year will see the first steps leading to the PC of the future.