Memory is very much like our brain as it is used to store data and instructions. Computer memory is the storage space where data is to be processed, and instructions needed for processing are stored. The memory is divided into a large number of smaller portions called the cell. Every cell/ location has a unique address and a size.
What is Primary Memory?
Primary Memory is the main memory of the computer system. Accessing data from primary memory is faster because it is an internal memory of the computer. The primary memory is most volatile, meaning data in primary memory does not exist if it is not saved when a power failure occurs.
Two types of Primary Memory are:
- RAM
- ROM
--> What is Random Access Memory(RAM)?
Random-access memory is a computer memory that can be accessed randomly; i.e. any byte of memory can be retrieved without affecting the preceding bytes.
Random-access memory is the common type of memory found in computer devices, for example, printers. Ram refers to Read and writes memory; means you can write data in RAM and also read data.
You already know that RAM is a volatile memory, which means that it requires a steady flow of electricity to maintain its contents. when the power is turned off, everything is in RAM is lost.
- RAM is further classified into two types- SRAM (Static Random Access Memory) and DRAM (Dynamic Random Access Memory).
Dynamic RAM (DRAM): DRAM is a type of physical memory used in most personal computers. The term dynamic shows that the memory must be continuously refreshed or it will lose its contents.
Static RAM (SRAM): Static random access memory is a type of memory that is faster and more reliable than the more common DRAM. Their name is static because they don’t need to refresh like DRAM.
Magnetoresistive RAM (MRAM): This a newer type of memory that stores data using magnetic charges instead of electrical charges. manufacturers say that MRAM has a larger storage capacity, fewer power consumables, and faster access times than other RAM. MRAM retains its contents after power is removed from the computer, Which saves our data after power loss means this is a type of Non-volatile RAM memory.
Types Of Dynamic RAM(DRAM)?
Conventional DRAM: This is the oldest and slowest DRAM technology. It uses the standard memory addressing method, where the first row and column be sent to the memory, and then the column address. But now this is not used on any new system and having replaced by others.
Fast Page Mode (FPM) DRAM: This is slightly faster than conventional DRAM. while DRAM needs that a row and column be sent for each access, FPM worked by sending the row address just once for many access to memory in a location near each other, improving access time. FPM is the slowest memory used in modern Personal computers.
Extended Data Out (EDO) DRAM: EDO also called hyper page mode DRAM. This is faster than FPM memory because of another transformative tweak in how the memory access work. EDO has had its timing circuits changed (modified) so one access to the memory can begin before the last one has completed. It gives a performance boost of around 3-5% over FPM in most systems.
Burst Extended data out (BEDO) DRAM: This is also an evolutionary improvement in conventional asynchronous RAM. EDO memory is merged with pipelining technology and special latches to allow for a much faster response time than regular extended data out EDO. BEDO memory allows the use of a much higher memory bus speed than EDO.
Synchronous DRAM (SDRAM): this is different from earlier types in that it does not run asynchronously to the system clock the way older, conventional types of memory do. SDRAM is tied to the system clock and designed to be able to read or write from memory in burst mode at 1 clock cycle per access at memory bus accelerate up to 100 MHz or higher. SDRAM accomplishes its faster access using a number of internal work improvements, including internal interleaving, which authorizes half of the module to start while the other half is finishing one.
Double data rate SDRAM (DDR SDRAM): this is similar to SDRAM, but doubles the bandwidth of the memory by transferring data twice per cycle on both the rising and falling edges of the clock signal. The clock signal transitions from “0” to “1” (rising edge) and then again back to “0” (falling edge) each cycle.
Direct Rambus DRAM (DRDRAM): DRDRAM works like an internal bus than a conventional memory subsystem. it is based around a direct Rambus channel, a highspeed 16-bit bus running at a clock rate of 400 MHz. As with DDR SDRAM, the transfer is accomplished on the rising and falling edges of the clock, yielding an effective theoretical bandwidth of approximately 1.6 GB/Second. This is a different approach, the way memory is currently worked over a wide 64-bit memory bus. DRDRAM is proprietary and is being designed to use a special type of module called Rambus inline memory module, Or RIMM.
Synchronous-Link DRAM (SLDRAM): SLDRAM improves the performance of the memory sub-system over SDRAM, The specification for SLDRAM call for a 64-bit bus running at 200 MHz clock speed. As with DDR SDRAM, a transfer is made twice on each clock cycle, for an effective speed of 400MHz. This yields a net theoretical bandwidth of about 3.2GB/second, double that of DRDRAM. Finally, SLDRAM is an open standard, meaning that no royalties need to be paid any more in order to make use of it.
Static RAM
Static RAM holds its data without any external refresh for a long time as power is supplied to the circuit. This goes against dynamic RAM (DRAM), the memory refreshed many times per second in order to hold and store its data contents. SRAMs have the following strength over DRAMs.
- Simplicity: SRAMs don’t need an external refresh circuitry in order for them to keep their data intact
- Speed: SRAM s faster than DRAM.
There are some following weaknesses of SRAMs over DRAMs.
- Cost: SRAM is a byte for byte, several times more expensive than DRAM.
- Size: SRAMs take more space than DRAMs.
--> What Is Read Only Memory(ROM)?
Types Of ROM
Programmable Read-only memory (PROM): PROM is able to re-programmed by using Prom Programmer. Generally, a PROM can be changed or updated only once.
Erasable programmable ROM (EPROM): This type of ROM can have its contents erased by ultraviolet light and then reprogrammed by a PROM programmer. This procedure can be carried out many times but the constant erasing and rewriting will eventually render the clip useless.
Electrically EPROM (EEPROM): This type of ROM works similar way to flash memory in which its contents can be flashed for erasure and then written to without having to remove the clip from its environment. EEPROMs are used to store the computer system BIOS and can be updated. *Flash memory – this is an uncommon type of EEPROM that can be erased and also reprogrammed in blocks rather than one byte at a time.
What is Secondary Memory?
All secondary storage devices which are capable of storing high volume data is referred to secondary memory. It's slower than primary memory. However, it can save a substantial amount of data, in the range of gigabytes to terabytes. This memory is also called backup storage or mass storage media.
Types of Secondary memory
Mass storage devices:
The magnetic disk provides cheap storage and is used for both small and large computer systems.
Two types of magnetic disks are:
- Floppy disks
- Hard disks
Flash/SSD
Solid State Drive provides a persistent flash memory. It's very fast compared to Hard Drives. Frequently found in Mobile phones, its rapidly being adopted in PC/Laptop/Mac.
USB drives:
It is one of the most popular types of secondary storage device available in the market. USB drives are removable, rewritable and are physically very small. The capacity of USB drives is also increasing significantly as today 1TB pen drive is also available in the market.
Optical drives:
This secondary storage device is from which data is read and written with the help of lasers. Optical disks can hold data up to 185TB.
Magnetic tape:
It is a serial access storage device which allows us to store a very high volume of data. Usually used for backups.
Characteristic of Primary Memory
- The computer can't run without primary memory
- It is known as the main memory.
- You can lose data in case power is switched off
- It is also known as volatile memory
- It is a working memory of the computer.
- Primary memory is faster compares to secondary memory.
Characteristic Secondary Memory
- These are magnetic and optical memories
- Secondary memory is known as a backup memory
- It is a non-volatile type of memory
- Data is stored permanently even when the power of the computer is switched off
- It helps store data in a computer
- The machine can run without secondary memory
- Slower than primary memory
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