RAM vs Cache memory | Difference between RAM and Cache memory

This page compares RAM vs Cache memory and mentions difference between RAM and Cache memory.

What is RAM ?

RAM is volatile memory. It does not retain data when power is turned OFF or fails. When computer is switched OFF, all the RAM data is lost. Hence when computer is turned ON again, BIOS reads OS (Operating System) and related files from HDD (Hard Disk Drive) and loads them back into RAM. RAM stores its data in series of memory cells which can be accessed in any order and hence the name Random Access Memory.

Following lines are provided on RAM to address.
CS : Chip Select
ADD : Address or location to read or write
WR : Write/Read , either set to 0 (for reading) or 1 (for writing)
DATA : n-bit data value to be saved in memory
OUT : n-bit Value stored at ADD

Example : 2²⁴ x 16 RAM which contains 2²⁴ or 16M words , each are 16 bits long.
RAM need 24 address lines. Its total storage capacity is 2²⁴ x 16 = 2²⁸ bits.

Following are the types of RAM.
• DRAM (Dynamic Random Access Memory)
• SDRAM (Synchronous Dynamic Random Access Memory)
• DRDRAM (Direct Rambus Dynamic Random Access Memory)
• SRAM (Static Random Access Memory)
• VRAM (Video Random Access Memory)
• Virtual Memory

What is Cache Memory ?

Cache memory is the memory which is located on the processor itself and it is used to make computer faster. The cache memory acts as buffer between CPU and RAM.
There are three types of cache memory which include L1, L2 and L2 >>.

Let us understand how it is useful with following steps.
• Step-1 : CPU requests for data.
• Step-2 : Cache returns the data if it is available in its storage. This makes process quicker. If it does not have it, it requests the data from RAM.
• Step-3 : RAM copies the data to the cache.
• Step-4 : The data is sent to CPU.

The larger the cache memory , the more the improvement in performance will be. Hence modern processors include up to 8 MB or more of cache memory. The figure-2 depicts comparison between RAM and cache (L1/L2) with respect to bandwidth, latency and size.

Difference between RAM and Cache Memory

Following table mentions difference between RAM and Cache memory.

Features	RAM	Cache Memory
• What is it ?	A form of data storage which stores data and machine code. It is used in any computer, laptop or mobile phone.	A component in computer which stores data so that future requests for that data can be served faster.
• Speed	Fast	10 to 100 times faster than RAM
• Capacity	More	Less
• Cost	High	Higher
• Application or usage	Operating Systems, Applications or programs, Data in use	Frequently used program instructions and data
• Types	DRAM, SRAM, MRAM	L1 cache, L2 cache, L3 cache

Also refer RAM vs ROM, MRAM vs SRAM vs DRAM which compares RAM versus ROM and mentions difference between RAM and ROM and RAM types.

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