Difference Between DDR2 and DDR1

The abbreviation for Synchronous Dynamic Random-Access memory is SDRAM. It can be clear by its name that it has synchronous behavior and synchronizes itself with the clock signal on CPU timing.


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SDRAM can be divided into two types viz. DDR SDRAM and SDR SDRAM.  

In this article, DDR SDRAM with its two versions is highlighted. The two versions are DDR2 and DDR1 in which DDR stands for Double Data Rate.

To service the computer then it becomes important to know the difference between DDR2 and DDR1.  

DDR2 vs DDR1 

The difference between DDR2 (Double Data Rate Version 2) and DDR1 (Double Data Rate) is that in DDR2 clock’s bus speed is twice that of the memory cells. Consequently, four words of data can transfer per memory cell cycle without speeding up the memory cells. DDR2 can operate the bus speed at twice compared to DDR1.  

DDR2 vs DDR1

The abbreviation for Double Data Rate Version 2 is DDR2. This RAM version was developed to attain a high data rate for transferring the block.

DDR2 replaced the older version DDR1, where the main changes made to the operational frequency between the prefetch buffer and the RAM chip and the amount of parameter is increased.  

The abbreviation for Double Data Rate is DDR. It is used in laptops, and computers and double data chunks are transferred to memory per clock cycle.

After the launch of DDR RAM, there are many upgrades in the market, such as DDR2, DDR3, DDR4. But all versions of DDR RAM failed to be compatible with the later or earlier RAM.  

Comparison Table

Parameters of ComparisonDDR2DDR1
Channel bandwidth3.20-8.50 GBps1.60-3.20 GBps
Bus clock speed200 MHz-533 MHz100 MHz-200 MHz
Internal banks4 or 84
Internal rate100-266 MHz100-200 MHz
Data strobesSingle-ended or differentialSingle-ended

What is DDR2? 

DDR2 SDRAM represents Double Data Rate 2 in which SDRAM is Synchronous Dynamic Random-Access Memory. In 2003, it replaced DDR SDRAM and in 2007, replaced by DDR3 SDRAM.

DDR2 DIMMs are not compatible with DDR and DDR3. The speed of DDR2 is 1066 MT/s, 800 MHz, 667 MHz, 533 MHz, and 400 MHz.

DDR2 allows for higher bus speed as well as the internal clock runs at half of the speed of the data bus and requires low power.

The two of the factors are produced by combing four data transfers total per internal clock cycle. In terms of supply voltage, DDR2 has a standard supply voltage as its 1.8V.

The internal clock of DDR2 runs at half the external clock rate of DDR1.

The memory modules of DDR2 with the top rating are at least twice as fast as memory modules of DDR1, which are best rated. DDR2 has a transfer speed that varies between 0.40- 1.06 GT/s (Giga transfers per second).

The commercially available DDR2 DIMMs have a maximum capacity of 8GB. However, support and chipset availability for those DMMs is sparse, and the more common 2GB per DIMM are used.

When it comes to reading latency, DDR2 has read latency of 3-9 clock cycles that is dependent upon setting. The internal rate for DDR2 is 100- 266 MHz.

What is DDR1? 

DDR SDRAM represents Double Data Rate in which SDRAM is Synchronous Dynamic Random-Access Memory. It is used in computers due to its class of integrated circuits memory.

DDR SDRAM is also widely known as DDR1 SDRAM. DDR1 was released in 1998 by Samsung and JEDEC. When it comes to supply voltage, DDR1 standard supply voltage of 2.5V

DDR SDRAM has many generations like DDR5 SDRAM, DDR4 SDRAM, DDR3 SDRAM, and DDR2 SDRAm. But its successors from backward or forward are inefficient to be compatible with DDR1.

This means that memory modules of DDR2 DDR3, DDR4, and DDR5 are failed to work in DDR1 equipped motherboards.

In comparison to SDR SDRAM or Single Data Rate SDRAM, with the strict control of the timing of the clock signals and electrical data, the interface of DDR SDRAM can make higher transfer rates.

To reach the needed timing accuracy implementations, often use schemes such as self-calibration and phase-locked loops. The modules of DDR1 are 200-pin SODIMM, 184-pin DIMM unbuffered, and 172-pin Micro DIMM.

The interface uses double pumping to double the bandwidth of the data bus but lacking a corresponding increase in the clock’s frequency.

With the down frequency of the clock, the advantage is that on the circuit board, the signal integrity requirements reduce which mainly connects the memory to the controller.

Main Differences Between DDR2 and DDR1 

  1. In terms of supply voltage, DDR2 has a standard supply voltage as its 1.8V. On the flip side, DDR1 standard supply voltage of 2.5V.  
  2. The DDR2’s transfer speed varies between 0.40-1.06 GT/s (Giga transfers per second), whereas the DDR1’s transfer for speed varies between 0.20-0.40 GT/s (Giga transfers per second).  
  3. The speed of DDR2 is 400 MHz, 533 MHz, 667 MHz, 800 MHz, and 1066 MT/s. On the other hand, the DDR1 are 200 MHz, 266 MHz, 333MHz, and 400 MHz. 
  4. The modules of DDR2 are 200-pin SODIMM, 240-pin DIMM unbuffered registered, and 214-pin Micro DIMM, whereas the modules of DDR1 are 200-pin SODIMM, 184-pin DIMM unbuffered, and 172-pin Micro DIMM.  
  5. When it comes to reading latency, DDR2 has read latency of 3-9 clock cycles that is dependent upon setting, whereas DDR1 has 2, 2.5, 3 clock cycles as its read latency. 
Difference Between DDR2 and DDR1


  1. https://cancerdiscovery.aacrjournals.org/content/1/1/78.short
  2. https://www.nature.com/articles/s41587-019-0224-x?_hsenc=p2ANqtz–g6Ln9XUyz2YtPsZXx0Op_Q-R6xpXqa4MCA9bwCgvqE5oL4CJ33z–iCqIjznQG9ewqDwQVZEUbAIdITH6IHYMKf2wWw&_hsmi=76370869
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