Origins of Flash Memory and RAM
Before diving into how flash memory and RAM differ, let’s first understand where each of these pivotal memory technologies originated.
The Invention of Flash Memory
Flash memory was invented in 1984 by Fujio Masuoka while working at Toshiba in Japan. At the time, electrically erasable programmable read-only memory (EEPROM) chips were commonly used for non-volatile storage. However these EEPROM chips could only erase data in blocks of 64KB at a time, making them painfully slow for many applications.
Masuoka aimed to improve this by inventing a new type of memory where data could be erased in smaller “flashes” – thus flash memory was born. His key innovation used a single transistor to store each bit, allowing data to be erased at much faster speeds down to the byte-level.
This made flash memory not only faster but cheaper and less power hungry than EEPROM. Masuoka presented his invention at the IEEE International Electron Devices Meeting in 1984 to widespread acclaim. Once introduced into the market, flash memory quickly became the standard storage choice for a vast array of consumer electronics like memory cards, USB drives and solid state hard drives. Even to this day, Masuoka’s flash memory remains a pivotal building block enabling our modern digital world.
The Creation of RAM
Unlike flash memory, the origins of random access memory (RAM) can be traced back to the earliest days of digital computing in the 1940s. Back then, cycles of access memory (CAM) and delays lines were two of the only ways to implement computer memory. However these technologies were painfully slow, complex and cost prohibitive.
In 1966, Robert Dennard at IBM Research invented a radical new type of memory built using semiconductor integrated circuits rather than magnetic cores. This allowed memory bits to be freely and easily accessed in any order, coining the term random access memory. Dennard also utilized a single transistor and capacitor to represent each bit, an approach still used in most RAM today.
His 1KB RAM chip was commercialized by IBM in 1967 and rapidly replaced earlier magnetic core and delay line memory types. Through gradual enhancements in speed, density and reduced costs, variations of Dennard’s original design now make up 95% of the RAM market. This includes dynamic RAM (DRAM) used for most system memory along with faster static RAM (SRAM) deployed for CPU caches. Without the advent of RAM, the foundation of modern computing may not even exist!
How Do Flash Memory and RAM Physically Work?
Now that we know the backstories of these monumental memory innovations, let’s explore what makes them tick from a technical perspective.
Inside Flash Memory
Flash memory stores data in an array of memory cells made up of floating-gate transistors. These specialized transistors contain two gates instead of one – a control gate and a floating gate. The floating gate is electrically isolated, allowing it to retain or lose electrical charges over long periods of time.
Each cell effectively acts as an electronic switch – when the floating gate has no charge current can flow, representing a binary 1. A charged floating gate blocks current flow, indicating a 0 instead. Flash memory is considered non-volatile because even if the power is cut, data remains safely stored in the floating gates ready to be accessed when power is restored.
To program (write) a flash cell, voltage is applied to the control gate while the power source and ground connectors are reversed from their read-mode orientations. This injects electrons from the transistor‘s source directly into floating gate, charging it negatively. Erasing is done by applying a positive voltage to the source while grounding the control gate, removing electrons from the floating gate through quantum tunneling. This allows flash memory to be easily rewritable by injecting/removing electrons into/from each floating gate as needed.
Inside RAM
The most common form of modern RAM is dynamic RAM (DRAM), making up over 90% of the market. DRAM uses a completely different approach than flash memory to store data without needing power to maintain it. It does this through a tiny capacitor paired with a transistor to make up a memory cell, together representing a single data bit.
The capacitor either contains an electrical charge to signify a 1 or remains empty showing a 0 instead. Because these capacitors naturally leak and lose their charge over time, the charge must be actively refreshed by brief current pulses around every 64 milliseconds. This constant refresh makes DRAM volatile since data is quickly lost without a power source. However it also makes DRAM very fast, cheap, and easy to implement at high densities.
DRAM memory cells are arranged in a large grid along what are called bitlines and wordlines. The transistor acts like a switch, choosing whether to connect the capacitor to be read/written when activated by its corresponding wordline. Sense amplifiers detect tiny voltage changes when the capacitor dumps its charge onto the bitline to read the stored bit. By utilizing an array of transistors and capacitors combined with control circuitry, many bits can be efficiently accessed in parallel.
Head to Head Comparison
Now that you understand what powers flash memory and RAM under the hood, let’s compare some of their key characteristics and capabilities side-by-side:
| Attribute | Flash Memory | RAM (DRAM) |
| Volatility | Non-volatile (retains data without power) | Volatile (requires constant power) |
| Speed | Slower – data written/read in pages & blocks | Very fast – data accessed randomly by word & bit |
| Physical Size | Very small and compact | Larger circuits required |
| Energy Usage | Lower power needs | Higher power consumption |
| Cost/GB (2022) | ~$0.40 per GB | ~$4.30 per GB |
| Rewrite Cycles | Finite (100k to 1 million) | Infinite |
A few key things stand out from this head-to-head overview:
- Flash provides permanent storage without power whereas RAM needs electricity to maintain temporary data used in current processes.
- RAM is exceptionally faster, accessing any random byte of data in nanoseconds. Flash read/write speeds depend greatly on the exact implementation but top out around 500MB/s.
- Flash memory is substantially less expensive per gigabyte compared to volatile RAM.
- RAM can be rewritten infinitely whereas flash cells wear out after hundreds of thousands of rewrites.
In summary – flash memory is used for slower yet permanent storage purposes while RAM provides ultra fast temporary runtime memory to execute programs.
Common Applications of Flash Memory and RAM
Given their distinctly different attributes, flash memory and RAM each excel in various applications across consumer and enterprise domains.
Where Flash Memory is Used
Flash memory offers compact, durable, shock-resistant portable storage at reasonably low cost and minimal energy use. This makes it the perfect choice for the following applications:
- USB Thumb Drives – Portable flash memory sticks for easily transferring and sharing files between devices and computers.
- Memory Cards – Flash-based storage cards used in digital cameras, mobile devices, and handheld gaming systems to hold photos, music, video and other media.
- Solid State Drives (SSDs) – Durable, compact and efficient alternative to mechanical hard disk drives (HDDs) for high speed storage without moving parts.
- MP3 Players – Apple iPods helped popularize flash-based music players with no fragile moving components.
Beyond consumer tech, industrial and commercial systems also frequently make use of flash memory’s benefits:
- Embedded Systems – Small inexpensive microcontrollers and SoC systems rely on onboard flash storage for programming and data-logging purposes.
- Automotive – Modern connected vehicle infotainment platforms integrate high reliability flash storage, even withstand extreme temperatures.
Essentially any application requiring compact, durable non-volatile storage can benefit greatly from flash memory technology. From home electronics to industrial equipment, flash enables functionality simply not possible with earlier storage mechanisms.
Where RAM is Used
As a form of temporary runtime memory rather than long-term storage, dynamic RAM dominates the following applications requiring instant data access:
- Personal Computers – All modern PCs whether desktops or laptops depend on DRAM as main system memory to load/run OS and applications.
- Smartphones/Tablets – Mobile devices also utilize DRAM paired with flash storage to enable smooth multi-tasking and quick app launching.
- Servers – Enterprise and cloud servers pack terabytes of DRAM for simultaneously serving countless users and customers.
- Specialized Graphics/Compute – High performance computing systems are often built around maximizing DRAM to feed data to GPU/TPU/FPGA processing elements.
Essentially all computing devices from microcontrollers to supercomputers are married to RAM as their main runtime workspace to load code/data then execute it as fast as possible. Without DRAM feeding their cores at rapid speeds, most processors would sit idle waiting on I/O.
The Future of Memory Technologies
Looking ahead, both flash storage and volatile memory face scaling and technological challenges prompting active R&D into potential next generation replacements.
What Comes After Flash?
As flash memory cells shrink below 20 nanometers, performance diminishes substantially and rewrite cycles are reduced. Alternatives like phase-change memory, ferroelectric RAM and even DNA storage aim to overcome flash limitations. Cost improvements must also be achieved to compete with extremely affordable flash solutions.
Many experts believe a hybrid storage hierarchy leveraging the strengths of multiple technologies will likely emerge rather than a single flash killer. For example, Intel and Micron’s 3D XPoint memory provides flash-like densities with DRAM-level speeds using an entirely new material composition – potentially revolutionizing future data centers!
What Comes After DRAM?
With DRAM technology becoming more complex as density growth slows and costs rise, memory makers also busily investigate options to replace today’s dynamic RAM. Options range from spintronics using electron spin rather than charge to manufacturing DRAM alternatives with resistive switching materials like phase-change, conductive bridging and other exotic substances.
Cost remains the supreme barrier as new memory innovations must equal DRAM’s rock bottom pricing to gain any adoption traction. Embedded, specialized applications are most likely to be the beachhead proving grounds putting next-gen RAM successors like MRAM, RRAM or NRAM through their paces.
Conclusion
In closing, while flash memory and RAM share the common purpose of storing binary data, they achieve this through very unique technical means optimized for vastly different use cases. Flash provides compact, energy efficient yet slower non-volatile storage while RAM serves up lightning quick temporary runtime memory.
Looking ahead, emerging memory technologies aim to overcome the scaling challenges faced by flash storage and decade-old DRAM technology. Yet replacing these entrenched, high volume incumbents will remain quite difficult unless breakthrough cost efficiencies can also be delivered.
One thing does seem certain – our civilization’s relentless appetite for instantly-available mountains of data will depend on continuing advances in underlying memory and storage for decades yet to come! Both researchers and tech giants alike continue pushing memory innovation forward to fuel tomorrow’s devices and infrastructure supporting our digital world.
