Significance of "Random" in RAM [Random Access Memory]

Re: What is the role of RAM in a computer?

ash

I thought I'd add in some additional questions, so our responses will be holistic.

Also, analogies are highly encouraged, just like MaRo has done.

- What is the significance of random in "RAM"?
- Differences between DRAM, SRAM and ROM?

This will definitely help answer question 2 😀

Bang!

Moving this to a separate discussion thread 😁 . Quite interesting, right?

Thanks, though I hoped those points will help others understand the "whys" of main memory of your original thread 😛

hi,

my point of view is that

As we know RAM is a kind of main memory which is much faster than auxilary memory (hard disk).But reason why ram is fast is because of access to any location in RAM is independent of it's location i.e random where as in hard disk it always depend upon the current position of read-write head so always delay is encountered in positioning the read-write head at required location .So "random" in RAM is because it takes almost same time to access any random memory location in RAM.

DRAM-these type of RAM contains data in form of charge stored in capacitor,but this charge always leak after specific time so DRAM always needs to be refreshed after every small intervals and its frequency can be 667Mhz ,800Mhz... (it is the frequency at which DRAM is refreshed).

SRAM-these type of ram are made of flip flops so here there is no fear of leakage of charge so there is no need of refreshing.That's the reason SRAM are sometime used as high speed cache memory.

correct me if i am wrong.

- Random :- means it can get the required data anywhere in its medium, opposed to "Sequential" which means you have to read all the data till the required point, which is sufficient for computer architecture, so Random is the efficient way for computer usage.

It satisfy the random concept by dividing the memory into addresses & fetch the required address directly.

what my Hardware nots says ( Given by my teacher in school) 😛

Memory is a workspace for Computers Processor
A Temporary Storage Area Where the programs and data being operated on by the processor must reside
It is called Random Access because you can randomly access any part of the memory (not sequentially)

Difference between DRAM , SRAM, and ROM

DRAM

It is dynamically accessed and is very dense very large data can be stored in very less space
It’s a bundle of capacitors which stores a charge to indicate a bit
the charge must be constantly refreshed else the electrical charge will be drained and data will be lost
Refresh occurs when the memory controller takes a tiny break and access all the rows of the data in the memory chip (controller is usually build in the north bridge of the mother board)

The refresh rate is usually 15MS (micro seconds)
That means every 15Ms all the rows in the memory are read to refresh the data which takes processors time
You can alter the refresh rate from BIOS but this could lead to soft errors
Modern systems don’t allow to change the refresh rate , the mother board usually read the refresh rate from the SPD (Serial Presence Detect) Rom found on the memory module and sets the cycling speed to match it )

Dram uses one transistor and capacitor pair per bit with a dense arrangement offering more memory capacity per chip they are usually arranged in a normal grid fashion
Each transistor reads the adjacent capacitor if the capacitor is charged the cell is read containing 1 else its 0
DRAM is much cheaper then the SRAM because of its dense nature where millions of capacitors can fit a real small space

SRAM

Static RAM is faster then the DRAM
SRAM uses a cluster of six transistors for each bit of storage , the usage of transistors instead of capacitors means no refresh is needed which makes it faster then the DRAM
Since SRAM uses 6 transistors for one bit storage the size of the chips are big
Bigger chips stores lesser data compared to DRAM size and storage capacity
More over they are more expensive then the DRAM

Physically SRAM is 30 times larger physically & 30 times more expensive then the DRAM
For Example DRAM of a given size can save up to 64Mb of data where as SRAM of same size can only save 2MB of data
SRAM takes only 2ms (micros seconds) to read data

Significance of "Random" in RAM
allow stored data to be accessed in any order (i.e.random).
The word random thus refers to the fact that any piece of data can be returned in a constant time,
regardless of its physical location and whether or not it is related to the previous piece of data.

DRAM
-Dynamic RAM has to be dynamically refreshed all of the time or it forgets what it is holding.
-has memory cells with a paired transistor and capacitor requiring constant refreshing.

SRAM
-a form of flip-flop holds each bit of memory
-A flip-flop for a memory cell takes four or six transistors along with some wiring, but never has to be refreshed. This makes static RAM significantly faster than dynamic RAM

ROM
-also known as firmware
-an integrated circuit programmed with specific data when it is manufactured.
-ROM chips are used not only in computers, but in most other electronic items as well.