How does DRAM work

Dynamic Random Access Memory (DRAM) works by storing and retrieving digital information in a volatile manner, meaning the stored data is lost when power is removed.

 

Here's a simplified explanation of how DRAM works:

 

1. Memory Cell Structure:

   • The basic unit of DRAM is the memory cell, which is typically a capacitor and a transistor. The capacitor stores the charge, representing a binary value (0 or 1), and the transistor acts as a switch, allowing the charge to be read or modified.

2. Row and Column Organization:

   • DRAM cells are organized in a two-dimensional grid, with rows and columns. Each intersection of a row and column forms a unique address, allowing the memory controller to access a specific cell.

3. Reading from DRAM:

   • To read data from a specific cell, the memory controller sends the row and column addresses to the DRAM module. The row address activates the corresponding row of cells (row activation), and the column address selects a specific cell within that row. The charge on the capacitor is then sensed, indicating the stored data (0 or 1).

4. Refreshing:

   • Unlike Static Random Access Memory (SRAM), which does not require periodic refreshing, DRAM cells need to be refreshed regularly. This is because the charge stored in the capacitors tends to leak over time. To prevent data loss, the memory controller reads the data from each row and immediately rewrites it, a process known as refreshing.

5. Writing to DRAM:

   • Writing data to a DRAM cell involves a process similar to reading. The memory controller activates the row, selects the column, and writes the new data by either charging or discharging the capacitor.

6. CAS (Column Address Strobe) Latency:

   • CAS latency is a measure of the time it takes between sending the column address and the data being available. Lower CAS latency values indicate faster access times. The memory controller must wait for the DRAM to perform various internal operations before the data is ready for reading or writing.

7. DDR (Double Data Rate) Operation:

   • In modern DRAM, data transfer often occurs in DDR mode, which means data is transferred on both the rising and falling edges of the clock signal. This effectively doubles the data transfer rate compared to the base clock speed.

8. Memory Modules (DIMMs):

   • DRAM chips are commonly integrated into memory modules, such as Dual In-Line Memory Modules (DIMMs). These modules are then installed on the computer's motherboard, providing the system with the required memory capacity.

 

In summary, DRAM works by using capacitors to store electrical charges, representing binary data. The memory cells are organized in rows and columns, and the memory controller coordinates the activation of rows and selection of columns to read or write data. Regular refreshing is necessary to compensate for charge leakage and maintain the integrity of stored data. While DRAM offers high-density storage and fast access times, it is volatile, requiring power to retain data.

 

Thank you.