RAM
The most familiar form of system memory, Random Access Memory (RAM) derives its name from the fact that any of its memory cells can be accessed directly if you are aware of the row and column that intersect at that cell. The columns are referred to as bitlines while the rows are referred to as wordlines. The intersection of a wordline and bitliine is the address of the memory cell onto a silicon wafer.

In case of Serial Access Memory (SAM), the opposite of RAM, the data is stored as a series of memory cells and can be accessed sequentially whereas data stored in RAM can be accessed in any order.

 


Some common types of RAM are as follows:

SRAM: Used primarily to create CPU’s speed-sensitive cache, Static Random Access memory (SRAM) uses multiple transistors for each memory cell. It does not have a capacitor in each cell.

DRAM: Dynamic Random Access Memory needs to be refreshed consistently and contains memory cells with a paired transistor. In order to activate the transistor at each bit in the column, DRAM sends a charge through the appropriate column (CAS).

SDRAM: Synchronous dynamic random access memory enhances the system’s performance by utilizing the burst mode concept.

FPM DRAM: The pristine form of DRAM, Fast Page Mode Dynamic Random Access memory waits through the process of locating a bit of data by column and row and then reading the bit and then starts on the next bit.

EDO DRAM: Contrary to FPM DRAM, Extended data-out dynamic random access memory does not wait and as the address of the first bit is located it starts looking for the next bit.

RDRAM: Rambus dynamic random access memory uses a special high speed data bus called the Rambus channel. It generates more heat than other chips as they operate at high speeds.

DDR SDRAM: Double data rate synchronous dynamic random access memory is somewhat similar to SDRAM but has higher bandwidth.

ROM

Read Only Memory (ROM) is an integrated circuit programmed with data that holds instructions for starting up the computer. Data stored in ROM is non volatile and is not lost when powered off. These data cannot be changed or a special operation is needed to be performed to change it.

PROM

Programmable read only memory (PROM) is a type of ROM. These chips are non volatile and cannot be purged to store something else once it has been used. Blank PROM chips can be coded with the help of a tool known as a programmer.

Similar to ROM, PROM chips also have a grid of rows and columns but here fuses connect the intersections.

EPROM

Erasable Programmable Read Only Memory can be erased with the help of ultraviolet light and rewritten many times. These chips are configured by the EPROM programmer, providing the voltage at the specified levels. The floating gate is linked to the row through the control gate. The cell has a value of 1 till the link remains established.

EEPROM

Electrically Erasable Programmable Read Only Memory chips are not required to removed to be erased or rewritten. These chips do not require to be erased altogether and specific portion of it can be easily altered. Additional dedicated equipment are also not required to change the content the EEPROM chips. These chips are erased and rewritten with the help of electric charge.