When you turn on your PC, the required driver and processes to boot up an Operating System will store in a temporary storage called RAM. The computer memory (RAM) is considered volatile memory, which means that the stored information is lost when there is no power. When you run a game, all the data needed for the game to run will be stored in RAM to be quickly accessible by CPU. The certain amount and speed of memory will increase the performance of your system in games. Let's look at both the memory size and speed and how they can affect the performance of your system in games.
Usually 4GB of memory is recommended for almost any modern games, keep in mind that the maximum allocated memory to a 32-bit process cannot go above 2GB, so if your game is running in 32-bit mode then maximum of 2GB can be used by the game. Do you really need more than 4GB memory when games are limited to use maximum 2GB of memory? Here I ran a test to see how the memory capacity will affect the performance in game.
My computer runs with 2x4GB memory. First I measured the amount of memory used by the system which was 1.5GB, then I ran the Half-Life 2 game at 1920x1080 maximum settings (no AA and AF was enabled) and measured the memory usage which raised to 2.3GB (HL2 uses 800MB of the system memory). I ran the test and then opened some photos in paint to fill up the memory as shown in table below then I recorded a 60 seconds benchmark at memory usage of 2.3GB, 4.4GB and 7.1GB. below you can see the results:
|RAM Usage||Avg FPS|
As you can see there is no performance loss even at 90% memory usage, so as long as you have sufficient memory to be allocated for game and operating system, adding extra memory will not increase the performance in games. Unless you do some video or photo editing works, adding extra memory beyond 8GB will not improve the performance in games but having more content cached by Operating System will benefit from the extra memory and increases the overall system performance. Also, you can use RamDisk utility to setup the extra memory space for games and applications and simply load the games into the memory to increase the data transfer rate and lifespan of your SSD or hard drive.
Memory speed and latency are the main factor to determine how fast is your memory. Memory modules are divided into DDR, DDR2, DDR3 and DDR4 categories which are developed based on SDRAM design. The I/O bus clock (known as rated clock) is controlled by the memory controller in your CPU or northbridge chipset. The memory has a different type of timing which indicates the speed to access each memory column (CAS) and row (RAS). CAS and RAS are measured in nanoseconds; the lower the value, the faster the RAM can be accessed.
Memory timing is usually shown by 4 numbers separated by (-); for example, 7-8-7-24. These numbers indicate the tCL-tRCD-tRP-tRAS latency of the memory. Usually, increasing the clock rate of the memory also increases the timing which may results in lower performance. RAMs designed for overclocking can keep the default timing at higher clock rates which guarantees the stability of the system. In real world tests, most games show very little improvement when the memory is overclocked or faster memory sticks are installed in the system. In other words, keep the standard memory speed your CPU supports and invest on better graphics card or CPU.