Difference between DDR1 DDR2 DDR3 DDR4

SDRAM stands for Synchronous Dynamic Random Access Memory. As the name suggests it has synchronous behaviour and as a result it synchronizes itself with CPU timing or clock signal. FOr example PC133 SDRAM refers to SDRAM running at the clock signal of 133 MHz. There are two types of SDRAM viz. SDR and DDR.

What is SDR SDRAM and DDR SDRAM ?

SDR SDRAM is the short form of Single Data Rate SDRAM. In this SDRAM type, same frequency is used for Input/Output operations, bus clock and internal clock. As mentioned above PC133 uses 133 MHz for all these purpose. SDR SDRAM can either read or write one at a time in single clock cycle.
DDR SDRAM is the short form of Double Data Rate SDRAM. It can transfer data on both the rising edge of the clock as well as falling edge of the clock i.e. doubles the transfer rate without even increasing the clock signal frequency. DDR SDRAM has 2 bit prefetch buffer size which is double of SDR SDRAM. There are various versions of DDR SDRAM viz. DDR1 (or simply DDR), DDR2, DDR3 and DDR4 based on various features as explained below.

DDR1 SDRAM or DDR SDRAM

Following are the features of DDR1 SDRAM type:
• It transfers data on rising and falling edge of clock. Hence it has data transfer rate double compare to SDR SDRAM type.
• Clock speed: 133 to 200 MHz
• Prefetch buffer size: 2 bits
• Operating voltage: 2.5V
• Data transfer rate: 266 to 400 MT/s (MegaTransfers per SECond)
• Examples: DDR266, DDR400

DDR2 SDRAM

Following are the features of DDR2 SDRAM type:
• It operates external data bus two times faster compare to DDR1 SDRAM type or DDR SDRAM.
• Clock speed: 133 to 200 MHz
• Operating voltage: 1.8 V
• Prefetch buffer size: 4 bits
• Data transfer rate: 533 to 800 MT/s (MegaTransfers per SECond)
• Examples: DDR2 533, DDR2 800

DDR3 SDRAM

Following are the features of DDR3 SDRAM type:
• Its power consumption is less compare to previous version i.e. DDR2 which is about 40% less. This is due to use of lower operating voltage of 1.5V compare to DDR and DDR2 SDRAM types.
• Operating voltage: 1.8 V
• Prefetch buffer size: 8 bits
• Data transfer rate: 800 to 1600 MT/s (MegaTransfers per SECond)
• DDR3L-800 , DDR3L-1066 , DDR3L-1333 and DDR3L-1600
• Special functions used: ASR (i.e. Automatic Self Refresh), SRT (Self Refresh Temperature).

DDR4 SDRAM

Following are the features of DDR4 SDRAM type:
• It provides further lower operating voltage and faster transfer rate compare to other DDR types.
• Operating voltage: 1.2V
• Data transfer rate: 2133 to 3200 MT/s
• Example: DDR4-2400, Micro Technology Inc.
• It processes four data in a single clock cycle.
• Efficiency: better than DDR3.
• Special functions: DBI (i.e. Data Bus inversion), CRC, CA parity

DDR1 DDR2 DDR3 DDR4 differences

Following table compares DDR1 vs DDR2 vs DDR3 vs DDR4.

The evolution from DDR1 to DDR5 demonstrates significant advancements in DRAM technology, providing improvements in speed, power efficiency and overall system performance.
Also refer DDR5 and LPDDR5 for their features and key differences.

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