Difference Between DRAM vs. Static random access(SRAM)

Intro

RAM is short term memory, that holds and stores data(instruction) that is currently in use.

DRAM vs static random access

DRAM and Static random access are the two main parts of RAM.

What is DRAM(Dynamic Random access memory)?

DRAM is random access memory made up of a transistor and capacitor. Together the transistor and the capacitor team up to create memory cells.

Inside a dram chip

Every memory cell in a DRAM chip holds a bit 1(on) and 0(off).

The two main parts

Transistor
The transistor is the switch which reads and controls the current flow of the capacitor.
If the current can flow through the transistor then it will hold the charge of 1(on). But if the current can’t flow through it holds the charge of 0(off).
Capacitor
The capacitor holds the charge of the transistor and reads the transistor. However, within the time the charges of the memory cells leak away.

Analogy

You can compare a bucket of electrons to a capacitor.
Inside of a bucket are electrons.
If the electrons store and charges a 1 in the memory cell, the bucket fills with electrons.
If the electrons store a 0, the bucket leaks and gets emptied. You can say bye bye electrons.
How to fix it and make it work?
The CPU or memory controller needs to come and say hey we are going to recharge all the capacitors holding a 1 before they are let go.
The Memory controller decides to read the memory it gets and then recharges it.

What’s the problem with DRAM

Since it has to be dynamically refreshed all the time it becomes slow.

What is Static random access?

Static random access is memory that never needs to be refreshed, unlike DRAM.
Static random access holds a flip-flop circuit.

Short introduction on flip-flop?

A flip-flop is a circuit that has two stable states.
On and off.
The circuit remains in one of the states until a signal causes it to switch.
Think:
You can think of it this way. Your light switch has circuitry. There is on and off.
You signal the light to turn it on if you want light. But what if you don’t want light. You signal the light to turn off.
Same as a flip-flop.

The benefit

A flip-flop circuit does not use a capacitor so it does not need to be recharged. Which makes static random access much faster.

Whats the problem with Static random access?

However, since static random access is using less memory per chip it makes it more expensive than DRAM.

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