Whenever you buy a computer or a smartphone, you come across terms like 2GB RAM, 4GB RAM, 16GB RAM, and so on.
What is RAM? What is its significance? How is it different from storage? Let us look at the concept of RAM in detail.
What is RAM?
RAM is an acronym for Random Access Memory. The name suggests that you access this memory at random. In other words, it is that part of a computer’s main memory that is directly accessible by the CPU.
RAM is a volatile memory. Hence, you will lose the stored information when you switch off the computer. The computers use RAM to store the data that the CPU is currently processing. Hence, the modifiable programs and data are stored in RAM.
We shall simply explain the concept of RAM. Let us suppose you are doing a mathematical calculation. There will be other simple calculations that are part of the main assignment. Usually, you have a rough piece of paper where you do these simple calculations using a pencil. Subsequently, you erase them and make the paper available for doing new calculations.
RAM is somewhat similar. It is a temporary memory. Once you accomplish the assignment, the memory is deleted so that you can proceed with your next operation.
Even as I type out the words in this article, it goes into the RAM initially. However, I keep on saving them so that I do not lose the data in case of an accidental switch-off of the computer.
This saved data goes into a separate memory known as a hard disk or other removable memory devices like USBs. It is a permanent memory as compared to the RAM which is temporary.
|Basic Document Editing||✓||✓||✓||✓||✓|
|Large Documents and Multitasking||X||X||✓||✓||✓|
|Basic Web Browsing||X||✓||✓||✓||✓|
|Heavy Web Browsing (20+ Tabs)||X||X||✓||✓||✓|
|Full HD Video Editing||X||X||X||✓||✓|
|Mid-Range Gaming with Old GPU||X||X||✓||✓||✓|
|High-End Gaming with Latest GPU||X||X||X||✓||✓|
Why do you need RAM if it is temporary?
That should be a good question. Yes, we need RAM because it is fast. The CPU can access this memory at random. You can write to and read data from RAM quickly as compared to ROM. Therefore, most of the systems run on RAM. When we save the data, it moves to the hard disk.
Different types of RAM
Fundamentally, RAM is of two types,
- Static RAM (SRAM)
- Dynamic RAM (DRAM)
We shall see the main differences between the two as we move along.
Static RAM – SRAM
As the name suggests, SRAM is static. However, it is also temporary because the data gets erased by switching off the power source. Thus, we can say that SRAM requires a continuous power supply to be functional. Since it is static, there is no need for refreshing the data being stored. Therefore, SRAM is useful for building Cache Memory.
SRAM uses transistors to store data. Therefore, it is comparatively expensive to DRAM. The advantages of SRAM are that it consumes less power and has faster access speeds. At the same time, the disadvantages are a higher cost of manufacturing and lesser memory capacities. Hence, you use SRAM in
- CPU Cache (L1, L2, L3)
- Hard drive buffer/cache
- DAC (Digital to Analogue converters) on video cards
Dynamic RAM – DRAM
As opposed to SRAM that remains static, DRAM is dynamic or changing RAM. Therefore, it requires periodic refreshing to function. Instead of two transistors that you have in SRAM, there is a capacitor in combination with a transistor in DRAM.
The capacitors discharge energy gradually thus entailing loss of data. Therefore, there is a need to refresh the data before it gets lost. It ensures that the data remains intact. You can compare the situation to a bucket having a hole at the bottom. As soon as you start filling water, the water drains away through the hole. You need to refill it continuously to ensure that you have water in the bucket at all times.
DRAM is also volatile. Therefore, it loses all the data when you switch off the power connection. The advantages of DRAM are lower costs of manufacturing and higher memory capacity. Compared to SRAM, DRAM is slower and consumes more power.
Typically, you use DRAM in
- System Memory
- Video Graphics Memory
In the early 1990s, you saw the evolution of the Extended Data Out Dynamic RAM (EDO DRAM) and Burst EDO RAM. Initially, these memory types were popular because of enhanced performance or efficiency at lower costs. However, with the arrival of the SDRAM, these memory types went into oblivion.
We have seen two fundamental types of RAM. The DRAM evolved into different types of RAMs as described below.
Synchronous Dynamic RAM (SDRAM)
DRAM is asynchronous. Therefore, it responds immediately to any data input. On the other hand, SDRAM is synchronous. It operates in sync with the CPU clock. It entails that it waits for the clock signal before responding to the data input.
The advantage of synchronous operation is that it allows the CPU to process overlapping instructions in parallel. You refer to it as ‘pipelining’ or the ability to read a new instruction before the resolution of the previous one. It does not affect the time taken to process transactions. However, it is beneficial because it allows for the completion of more instructions simultaneously.
When it processes one read and one write instruction per clock cycle, it results in a higher overall CPU performance rate. SDRAM supports such pipelining because it divides the memory into separate banks. Therefore SDRAM has wide acceptance as compared to the DRAM.
SDR SDRAM – Single Data Rate Synchronous Dynamic RAM
SDR SDRAM is the same as SDRAM. It is only an expanded form to differentiate from DDR SDRAM. The single data rate indicates how the memory processes one ‘read’ and one ‘write’ instruction per clock cycle. It helps to clarify comparison with DDR SDRAM.
DDR SDRAM – Double Data Rate Synchronous Dynamic RAM
DDR SDRAM is similar to SDR SDRAM. The only difference is that it is twice as fast. Therefore DDR SDRAM can process two ‘read’ and two ‘write’ instructions per clock cycle. The functions are similar, but they have physical differences.
The SDR SDRAM has 168 pins and two notches on the connector as compared to 184 pins and a single notch on the DDR SDRAM.
Also, DDR SDRAM works at a lower standard voltage (in the range of 2.5 V from 3.3 Volts) thereby preventing any backwards compatibility with SDR SDRAM.
There are three variants of DDR SDRAM.
It is an evolutionary upgrade to DDR SDRAM. It is faster as compared to DDR SDRAM. While DDR memory modules maximise at 200 MHz, the standard DDR2 memory modules top out at 533 MHz It runs at a lower voltage of 1.8 Volts, and has more pins (240) to prevent backwards compatibility.
It is an improved version of the DDR2 because of the advanced signal processing, higher memory capacity, higher clock speed (up to 800 MHz), and lower power consumption (1.5 Volts). It has an equal number of pins as the DDR2, but the other advantageous aspects prevent backwards compatibility.
As compared to the DDR3, the DDR4 is an improved version. You can experience it in the form of advanced signal processing (reliability), more memory, lower power consumption (1.2 Volts), and faster standard clock speeds (up to 1600MHz). The DDR4 uses a 288-pin configuration to prevent backward compatibility.
GDDR SDRAM – Graphics Double Data Rate Synchronous Dynamic RAM
GDDR SDRAM is a specific type of DDR SDRAM designed for rendering video graphics, usually in combination with a dedicated GPU (Graphics processing unit) on a video card.
The modern PC games exhibit incredibly realistic HD environments. Therefore, they require significant system specifications and the best video hardware to play. It is especially when you use 720p or 1080p high-resolution displays.
As you see in DDR SDRAM, GDDR SDRAM has its evolutionary line such as GDDR2 SDRAM, GDDR3 SDRAM, GDDR4SDRAM, and GDDR5 SDRAM. As you move higher, you get more improved performance and lower power consumption.
Though DDR SDRAM and GDDR SDRAM are similar in many ways, they are not the same. GDDR SDRAM operates by processing massive amounts of data but at comparatively lower speeds. On the other hand, DDR SDRAM favours speed (latency) over data (bandwidth).
Other Types of DRAM
Rambus DRAM (RDRAM)
As compared to a small CPU-memory bus, the RDRAM provides a very high data transfer rate. Having a data bus width of 8 or 9 bits, the RDRAM uses various speed-up mechanisms like synchronous memory interface, caching inside DRAM chips, and fast signal timing.
Fast Page Mode DRAM (FPM DRAM)
The FPM DRAM was the original form of DRAM. It waits through the entire process while it locates a bit of data by column and row, and then reads the bit before proceeding on to the next bit. The maximum transfer rate to the L2 cache is around 176 Mbps.
Cache DRAM (CDRAM)
The CDRAM is a specific DRAM with an on-chip cache memory (SRAM) that acts as a high-speed buffer for the principal DRAM.
Credit Card Memory
The Credit Card memory is a proprietary self-contained DRAM memory module that you can plug into a particular slot for use in notebook computers.
PCMCIA Memory Card
It is another kind of self-contained DRAM module for notebooks. These are not proprietary cards and hence should work with any notebook provided the system bus matches the memory card’s configuration.
Other types of memory
Your computer uses a small amount of memory to remember things like hard disks settings and so on. It uses a small battery to provide it with the power it needs to maintain the memory contents.
Flash memory is entirely different from SDR and DDR in the sense that it is a non-volatile storage medium. It retains all data even after you shut off the power connection. It is similar to the solid-state drives (SDDs). The following appliances use Flash memory.
- USB Flash Drives
- Memory cards
- Portable media players
- Small electronic toys
Read Only Memory (ROM)
We have seen different types of RAM. Now, let us explore some types of ROM. We have discussed that RAM is a volatile memory that is not capable of storing data on a permanent basis. On the other hand, ROM is a non-volatile memory.
Hence, it is possible to save information even after switching off the power source. However, you cannot write data on a ROM. The manufacturers decide the contents of the ROM.
There are different types of ROM.
It is Programmable ROM. The user can store permanent data in a PROM. You can feed data into it using PROM programs.
The EPROM is an erasable PROM. You can erase the stored data by exposing it to UV light for about 20 minutes. You have to remove the EPROM IC and expose it to UV light to erase data. However, you can erase selective data. You have to delete the entire data. EPROMs are cheap and reliable.
It is Electrically Erasable PROM. You can erase the chip and program it again on the board easily byte by byte. It should take a few milliseconds to wipe data. However, you can reprogram the EPROM for a maximum of 10,000 times only.
How much RAM do I need?
It depends on what you wish to do with your computer or laptop. However, one of the first things you do when purchasing a new PC/laptop is to check out the RAM.
We have seen various aspects of RAM and discussed the minimum RAM you need depending on how you plan to use your computer. Choosing the right laptop/PC should not be a problem for you any more, at least as far as RAM is concerned.
The difference between RAM and Storage
Many people confuse memory and storage. Maybe, it is because the units of measurement are the same (MB, GB, TB). Remember, RAM is synonymous with the main memory where the computing systems store data that it is using actively.
Storage systems such as hard drives, USB devices, network storage devices, cloud storage, and so on are places where the system saves data for accessing at a later stage.
The advantage of RAM is that computers access data from RAM very quickly. However, when there is a shut-down of the system, the data is lost. However, it is not the case with storage. You can retrieve a document from the hard disk after restarting the computer.
As far as cost is concerned, storage is less expensive than RAM. Hence, you have PCs and smartphones with more GB storage than RAM.
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