Recent Advancements in Memory and Storage: A Tech Talk

A Summary of the Samsung Tech Talk on Device Memory and Storage held during Probe 2019

In this article, we are going to take a look at two of the technological age’s most important inventions — Memory and Storage.

Without them, none of the technological marvels that we witness today would have been possible to achieve. Memory technology has come a long way from the ancient vacuum tubes to today’s Cloud technology.

Memory is evaluated using three main parameters:

1. Bandwidth — This is the rate at which data can be read from or stored into semiconductor memory by a processor. This is generally expressed in bytes/second.
2. Latency — This refers to the delay that occurs in data transmission as the data moves from the computer RAM to the processor.
3. Reliability — This refers to the consistency with which the data is transmitted.

Basic DRAM Architecture:

Dynamic random-access memory (DRAM) is a type of random access semiconductor memory that stores each bit of data in a separate tiny capacitor within an integrated circuit. The capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1.

Basic structure of a DRAM cell array

Double Data Random Access Memory(DDRAM): DDRAM is a type of Random Access Memory which operates with higher transfer rates and better performance compared to earlier RAM modules. It is used in desktops and servers.

DDRAM is easily scalable and replaceable but requires more complex cooling systems.

A number of memory solutions are possible using the Double Data Rate (DDR) module. Some of these are discussed below:

1. LRDIMM(Load Reduced Dual Inline Memory Module): The LRDIMM technology ensures that the bus connecting the controller to the DIMMs do not face excessive loading.

2. Low power DDR: This technology is mainly used for embedded applications. It has a smaller area and is mainly focused on saving power.

3. Graphics DDR: The Graphics DDR is high performance and is primarily used in Graphic Processing Units(GPUs). GDDR6 is currently under development.

High Bandwidth Memory: Performance of the memory is enhanced through 3D stacking of DRAM dies, connected through TSVs(Through Silicon Vias).It has a drawback in the fact that manufacturing it is expensive.

Current Storage Space Scenario:

The difference between storage and memory lies in the fact that storage of data refers to the non-volatile aspect whereas memory is volatile.

Storage technologies mainly use flash cells . Flash memory is an electronic (solid-state) non-volatile computer storage medium that can be electrically erased and reprogrammed. The flash cells generally used are either of NAND flash or NOR flash. NOR flash is generally used for code storage whereas NAND Flash is more suited for data storage.

NAND Flash: NAND Flash cells are constructed by using two overlapping gates, with floating gates surrounded by oxide. The isolated gate makes an excellent trap for electrons, which can be retained for years.

NAND Flash technology is operated in four modes: SLC mode, MLC mode TLC mode and QLC mode.

The SLC mode: Under SLC mode, only 1 bit is stored per cell. Erase time is about 1.5–2 ms. Once a cell is programmed using SLC operation, it can only be read in SLC mode.

The MLC mode: Each cell stores a 2 bit value, increasing density with the same die size. This is done by manipulating bit line voltages across the NAND array.

The TLC mode: Under this mode, 3 bits are stored per cell. It has an erase time of 4.5ms.

The QLC mode: 4 bits are stored per cell.

Storage Solutions for Embedded Applications:

1. UFS: This technology is mainly used in smartphones. It provides high performance in mobile systems.
2. eMMC: The term eMMC is short for “embedded Multi-Media Controller” and refers to a package consisting of both flash memory and a flash memory controller integrated on the same silicon die.
3. The Solid State Drive(SSD): The solid state drive is one of the most widely adopted technologies for storage . It presents a multitude of benefits which makes it superior. The SSD is made of three components: NAND Flash, DRAM and an SSD controller.

SSD is faster, compact, more power efficient and more silent compared to other technologies. It also provides higher throughput.

Applications of SSD includes gaming, content creation, cloud computing and virtualization among other uses.

What does the future hold for memory and storage technologies? With the advent of the Internet of Things (IoT), a variety of needs are required to be met. Faster data transfer, low latency and increased bandwidth are some of the requirements that will have to be met. Computer Architecture will have to compensate for the slowing down of Moore’s Law.

The boom in Big Data also fuels the need for more memory and storage bringing them to the forefront of semiconductor driven growth.

This article is a compilation of the major points discussed during a tech talk held by Samsung India during the last edition of Probe, under the Throwback Thursday series. Say tuned for more such nuggets of knowledge, and do mark your calendars for Probe 2020!