What Is A Random Access Memory – Intro
What is a Random Access Memory (RAM)? It is a memory which is used to store data for fast access by the CPU.
Note : This post is about DRAM which is the main system RAM. If you want to learn about Static Ram, check this link.
Question 1 : Why RAM exists?
Because the Hard Drive is slow and the CPU needs to communicate in speed with someone in its league.
If it doesn’t, it will wait “forever” for the disk to send the data.
You need to sign hundreds of fan letters. You are in your room and you have a chair and a desk(with drawers) to sit and sign. You have a friend downstairs that has all the hundreds of fan letters.
Your friend knows you have a desk with drawers so he brings you as many letters as your drawers can fit. Your friend is busy too so when you call him/her , he/she cannot service you right away.
When it’s time to service you, he/she will bring you enough letters that will fit in the drawers. If you hadn’t got a chair and a desk with drawers, he/she would bring you one at a time because he/she knows you don’t have a chair and a desk.
In this analogy,
the chair and desk plays the role of RAM,
you play the role of CPU,
and your friend plays the role of the Hard Drive.
Question 2 : The more RAM the faster the PC gets?
Most of the time the answer is No. Below we list the case where is it yes.
Example of Yes: You have 2GigaBytes RAM installed in your PC. Your new cool game requires 2.5 GigaBytes. What will happen: in order to load that 500 Megabytes, your system will take 500 Megabytes from your RAM and store it the Hard Drive.
Then will load the new 500 Megabytes that wanted to load from the start and store them in RAM so it can access it faster. But those 500 Megabytes tha were first in the RAM and saved to disk will be probably be needed in a short amount of time.
So this process of Swapping from RAM to disk is going to happen very often because all these data is needed frequently (that’s why they were in the RAM in the first place).
And as you know, the Hard Drive is very slow compared to RAM. And your game that is waiting to get the data will wait for these transfers all the time.
And this Swapping will make your PC very slow.
This is a simplified example but that’s what the operating system does generally when it has no RAM to store data.
So a good practice is to not push the RAM to its limits because the operating system might start doing swaps before reaching 100%.
Example of No: You have 8 GigaBytes of RAM and your game requires 4GB. There is plenty of room in the RAM to store your game and maybe more programs so if you buy another 8 GB it won’t do anything to your game speed (neither your graphics will be better or your gameplay be smoother). You will just be able to open more windows and programs.
Question 3 : What is the recommended RAM for today’s games?
The recommended RAM is 8GB.
So if you currently have 8GB or less, you can always add another 8GB or more chip.
Note : If your RAM is DDR3, you must also put another DDR3.
Also if your RAM is DDR4, you must put another DDR4.
If you are buying a new laptop or desktop, buy DDR4 (DDR3 is old and slow – i have DDR3 and i bought my PC in 2010).
Question 4 : What is Dual Channel RAM?
Dual channel RAM is when you put 2 RAM modules of the same brand and same frequency in 2 slots designed for dual channel architecture.
These RAMs then work together to transfer data at a faster pace (than single channel).
Note: the system (the motherboard mainly) must support this technology in order to reap the benefits of it. Otherwise it is like 2 normal RAMs in 2 different slots.
Let’s see a video related to dual memory channel.
Dual Channel VS Single Channel Video
Of course there is a triple and quad memory channel architecture (at least that’s what i’ve seen in desktop computers).
If you put a single RAM module in a dual channel memory slot, there is no problem.
Usually in the motherboard there are color indicators (and maybe textual indicators) that state the dual or more memory channel architecture.
Question 5 : How RAM frequency affects perfomance?
Long story short, the higher the RAM frequency doesn’t mean the higher the speed.
There is a metric called CL (CAS Latency – Column Access Strobe Latency) that affects the RAM speed quite significantly. Let’s see a piece from a good post :
“The maximum bandwidth can be calculated using four factors:https://www.pcsteps.com/7932-real-ram-speed-mhz-cas-latency/#How_the_RAM_frequency_in_MHz_sets_the_bandwidth
The RAM’s DRAM clock frequency
This is the frequency of RAM, in MHz. One Hertz (Hz) is a single clock cycle per second. 1MHz is 1,000,000Hz.
The number of data transfers per clock cycle
In all current RAM, there are two data transfers per clock cycle. This is where the name the Dual Data Rate (DDR) originated.
The memory bushttps://www.pcsteps.com/7932-real-ram-speed-mhz-cas-latency/#How_the_RAM_frequency_in_MHz_sets_the_bandwidth
In every motherboard from the past decade or so, the memory bus is 64 bit.
The number of interfaces
The interfaces express how many data channels can work at the same time. If we install one RAM module, we have a single data channel. If we install two modules in Dual Channel DDR, we have two channels. “
“When the memory controller commands RAM to read a specific memory column, the RAM’s reaction is not instantaneous. There is a delay between the command to read the targeted part of the memory and before the first bit of the data reaches the exit pins. This delay is named Column Address Strobe (CAS) Latency. As with any delay, the lower this number, the better. “https://www.pcsteps.com/7932-real-ram-speed-mhz-cas-latency/#CAS_Latency_The_real_RAM_speed
You can find the real speed of the RAM by dividing the original frequency by 2 (because DDR RAMs do 2 transfers per cycle) and then divide the remaining by the CL. But :
“The thing is, it’s not a good idea to compare RAM of different architecture just based on the frequency and the CAS Latency.https://www.pcsteps.com/7932-real-ram-speed-mhz-cas-latency/#Does_DDR3_have_a_faster_RAM_speed_than_DDR4
DDR4 RAM includes new technologies, which speed up the function of the RAM even with a higher CAS Latency “
So use the above calculation for same architecture memories.
Unfortunately, this theory doesn’t apply well if you consider the following video.
RAM Frequency YouTube Video
Well, from the 2133 Hz to the 3000Hz there is a less than 10% increase in FPS. But the price is not only 10% more so choose accordingly.
Conclusion – What Is A Random Access Memory
That’s all for now. If you think something is missing and can be improved, you can drop a comment below.