Decoding DDR Memory Organization: Understanding 1Gb DDR2 SDRAM Datasheet

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In summary, the 1Gb DDR2 SDRAM is organized into rows, columns, and banks. The 1Gb is equal to 64Mb*16 datalines, which is equivalent to 8Mb*8 banks*16 datalines. The 8Mb is derived from the 13 row address lines and 8 column address lines, which results in 8192*256 = 2Mb. Additionally, each bank is organized as 8192 by 256 by 64 bits, with 10 column select bits but only 8 being used to select the column. Precharging a row is necessary before selecting it in order to ensure the correct 16 bit word is selected from the 64 bit bank output
  • #1
likephysics
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I was going through the datasheet of 1Gb DDR2 SDRAM. It's organized in rows, columns and banks.
The 1Gb is actually 64Mb*16 datalines.
Which is 8Mb*8 Banks * 16 data lines
I can't figure out how they got 8Mb?

In the datasheet block diagram (attached), there are 13 row address lines. So 2^13 = 8k
there are 8 column addr lines, so 2^8 = 256
8192*256 = 2Mb ?
 

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  • #2
Hi likephysics. Each bank is actually organized as 8192 by 256 by 64 bits. There are 10 column select bits, but only 8 of them are used to actually select the column. The remaining 2 are used to select the correct 16 bit word from the 64 bit bank output.
 
  • #3
uart, Thanks.
One more DDR question - why do you need to precharge a row before selecting it?
 

Related to Decoding DDR Memory Organization: Understanding 1Gb DDR2 SDRAM Datasheet

What is DDR memory organization?

DDR memory organization refers to the way in which data is stored, accessed, and managed in Double Data Rate (DDR) memory modules. This includes the physical layout of the memory chips, the timing and synchronization mechanisms, and the protocols used for data transfer.

How is DDR memory organized?

DDR memory is organized into ranks, banks, and rows and columns. Ranks refer to independent sets of memory chips, while banks are subdivisions within a rank. Rows and columns refer to the physical location of each bit of data within a bank.

What is the difference between DDR3 and DDR4 memory organization?

The main difference between DDR3 and DDR4 memory organization is the number of banks. DDR3 memory typically has 8 banks per rank, while DDR4 memory has 16 banks per rank. This allows for faster access to data in DDR4 memory.

How does DDR memory organization affect performance?

DDR memory organization can greatly impact the performance of a computer system. A well-organized memory layout can result in faster data transfer speeds and improved overall system performance. Additionally, the number of banks and the timing of data transfer can also affect performance.

What factors should be considered when designing DDR memory organization?

When designing DDR memory organization, factors such as the intended use of the memory, the speed and capacity requirements, and the compatibility with other components in the system should be taken into consideration. Additionally, the physical layout of the memory chips and the timing and synchronization mechanisms should also be carefully planned for optimal performance.

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