RANDOM ACCESS MEMORY (RAM)
RAM which stands for random access memory. It’s one of the most critical elements in every computing device. RAM is a temporary memory bank where the computer stores data it needs to retrieve quickly. RAM keeps data that is easily accessible to the processor so it can quickly find it without having to go into long-term storage such as hard disk drive or flash drive, to complete the immediate processing tasks.
RAM is present in all the computing devices, whether it’s a desktop computer, a tablet/smartphone, or even smart electronic devices (smart watch) and IoT computing devices. Mostly, all computers have a way of storing information for longer-term access, too. But the memory needed to run the application’s processes you’re currently working on is stored and accessed in the computer’s RAM.
Function of RAM in our Devices
RAM is a form of temporary storage that gets wiped off when the computer is turned off, or when the power from the computer goes down. RAM offers lightning-fast data access, which makes it ideal for the undergoing processes, apps, and programs the computer is currently working on, such as the data needed to stream the online video through web browser.
To understand how RAM operate, we have to first understand how it manipulates the ins and outs flow of electricity that represent all the data/information inside the computer system.
Assigning/Writing Data to RAM
Software, in combination with the operating system, sends a burst of electricity along an address line; An address line is a microscopic strand of electrically conductive material etched onto a RAM chip – a very tiny integrated circuit. Each address line identifies the location of a spot in the chip where data can be stored. The burst of electricity identifies where to record data among the many address lines in a RAM chip.
The electrical pulse turns on (closes) a transistor that’s connected to a data line at each memory location in a RAM chip where data can be stored; A transistor is essentially a microscopic electronic switch.
NPN Transistor of RAM
While the transistors are turned on, the software sends bursts of electricity along the selected data lines. Each burst represents a 1 bit. The 1-bit and the 0-bit make up the native language of processors, commonly called the machine language. Bit is the most basic unit of information that a computer manipulates.
When the electrical pulse reaches an address line where a transistor has been turned on, the pulse flows through the closed transistor and charges a capacitor; Capacitor is an electronic device that stores electricity. This process repeats itself continuously to refresh the capacitor’s charge, which would otherwise leak out. When the computer’s power is turned off, all the capacitors lose their charges. Each charged capacitor along the address line represents a 1 bit. An uncharged capacitor represents a 0 bit. The computer uses 1 and 0 bits as binary numbers to store and manipulate all information, including the texts, graphics, and even the sound.
Logical Structure of RAM Capacitor
OBTAINING/READING DATA FROM RAM
When software needs to get data stored in RAM, another electrical pulse is sent along the address line, once again closing the transistors connected to it. Everywhere along the address line that there is a capacitor holding a charge, the capacitor will be discharge through the circuit created by the closed transistors, sending electrical pulses along the data lines.
The software recognizes from which data lines the pulses come and interprets each pulse as a 1. Any line on which a pulse is lacking, indicates a 0. The combination of 1s and 0s from eight data lines forms a single byte of data. A byte can be used to hold the information of a single character or symbol, such as the letter X.
DATA TRANSPORTATION FROM RAM CHIPS TO CPU AND VICE-VERSA
No matter how fast a processor can be, it’s limited by how fast memory feeds them data. Traditionally, the way to pump out more data to CPU was to increase its clock speed. The clock speed measures the number of cycles CPU executes per second. With each cycle, or tick, of the clock regulating operations in the processor and movement of memory data, synchronous dynamic random access memory (SDRAM) memory could store a value or move a value out and onto the data bus headed to the processor. But the increasing speeds of processors outstripped that of random access memory (RAM). Random Access Memory design narrowed the gap in two ways. One is to double data rate (DDR). Previously, a bit was put or gotten on each cycle of the clock. It’s as if someone loaded cargo (putting data) onto a train traveling from X-city to Y-city, unloaded that cargo (getting/offload the data), and then had to send the empty train back to X-city again, despite having a free cargo in Y-city that could hitch along for the return trip. With DDR, a handler could unload that same cargo when the train arrives in Y-city and then load it up with new cargo before the train makes its journey back to X-city. This way, the train is handling twice as much traffic (data) in the same amount of time. Substitute memory controller for the persons loading and unloading cargo and clock cycle for each round-trip of the train, and you have DDR. Another change to RAM, DDR2, which doubled the data rate in a different way. It cut the speed of memory’s internal clock to half the speed of the data bus. DDR2 quickly evolved into DDR3, and then to DDR4, each halving the clock rate of its predecessor. A significant impact to cutting memory speed is that the RAM uses less electricity, and it also pays off with cooler running, more reliable memory chips.
Example of personal computer random access memory (RAM).
Image credit: By An-d - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27224495
FLASH MEMORY
If you are using a DESKTOP or LAPTOP computer, data in RAM that’s not saved to storage drive disappears when the computer is turned off. But computers that have evolved into smartphones, tablets, smartwatches, cameras, and other handhelds don’t have hard-disk drives for data storage. These devices also use memory chips for storing information, but yet when you turn off the smartphone, all the contacts, music, pictures, videos, and apps would still be there when the phone is turn on back again. All the recent computers that evolved latest technology don’t used same technology architecture as in ordinary RAM for the Desktop/Laptop computers. Instead, they used flash memory technology that freezes data in place.
Flash memory is a data-storage medium used with computers that have evolved into smartphones, cameras, and other electronic devices. Unlike previous forms of data storage, flash memory is an EEPROM (electronically erasable programmable read-only memory) form of computer memory and thus does not require a power source to retain the data.
HOW FLASH MEMORY HANDLES and PROCESS DATA
Flash memory is normally laid out along a grid of printed circuits running at right angles to each other. In one direction, the circuit traces are word addresses; circuits at a right angle to them represent the bit addresses. The two addresses combine to create a unique number address called a cell.
The cell contains two transistors that together determine if an intersection represents a 0 or a 1. One of the transistors called the control gate is linked to one of the passing circuits called the word line, which determines the word address.
A thin layer of metal oxide separates the control gate from the second transistor, called the floating gate. When an electrical charge runs from the source to the drain, the charge extends through the floating gate, on through the metal oxide, and through the control gate to the word line.
A bit sensor on the word line compares the strength of the charge in the control gate to the strength of the charge on the floating gate. If the control voltage is at least half of the floating gate charge, the gate is said to be open, and the cell represents a 1. Flash memory is sold with all cells open. Recording to it consists of changing the appropriate cells to zeros.
Flash Memory
Flash memory uses Fowler Nordheim tunneling to change the value of the cell to a zero. In tunneling, a current from the bit line travels through the floating gate transistor, exiting through the source to a ground.
Energy from the current causes electrons to boil off the floating gate and through the metal oxide, where the electrons lose too much energy to make it back through the oxide. The electrons are trapped in the control gate, even when the current is turned off.
The electrons have become a wall that repels any charge coming from the floating gate. The bit sensor detects the difference in charges on the two transistors, and because the charge on the control gate is below 50 percent of the floating gate charge, it is considered to stand for a zero. When it comes time to reuse the flash memory, a current is sent through in-circuit wiring to apply a strong electrical field to the entire chip, or to predetermined sections of the chip called blocks. The field energizes the electrons, so they are once again evenly dispersed.
Flash memory comes in a variety of configurations, including SmartMedia, Compact Flash, and Memory Sticks (used mainly in cameras and other smart electronic devices). There’s also USB-based flash drives (also called thumb drives and flash drives), memory cards use flash memory technology to store and move data around. The form factors, storage capacities, and read/write speeds vary. Some include their own controllers for faster reads and writes.
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