DDR2 Memory 800 MHz: Calculating Data Transfer in Bits vs MB

[biferi]

I know if I have a DDR2 Memory that is 800 MHz and it is 64 Bit the math to findout the Data Transfer is

800,000,000 X 64 = Data Transfer.
But will this give me the Data Transfer in just Bits Per SEC. or MB Per SEC?

 

[jedishrfu]

This might help:

http://en.wikipedia.org/wiki/DDR_SDRAM

so for DDR-400
200 MHz clock --> 400 MHz data rate
8*400 MHz --> 3200 MB/s

so in your case 800 *8 -> 6400 MB/s

 

[biferi]

I did have a look at your link and I think this got me more confused.

If I want to know my Transfer Rate for my DDR2 800MHz 64 Bit DiMM in Bytes I do the math like this

800MHz X 64 then take the out come and Divid by 8

Will give me Transfer in Bytes per sec Right?

 

[jedishrfu]

I did have a look at your link and I think this got me more confused.

If I want to know my Transfer Rate for my DDR2 800MHz 64 Bit DiMM in Bytes I do the math like this

800MHz X 64 then take the out come and Divid by 8

Will give me Transfer in Bytes per sec Right?

Yes, that seems right. I gave you the link because it had several tables where the Hz was listed along with the MB/sec to give you a comparison and perhaps help answer other related questions.

I noticed that a given Hz was doubled because the memory is read on the up cycle and on the down cycle of the clock signal. If the memory is transferred in parallel on a 64 bit or larger bus then your answer 800 * 8 is the MB/sec speed is correct but if say the data was transferred on a smaller 32 bit bus then the rate would be half or 800 * 8 / 2 MB/sec.

 

[LudusRex]

The equation you have provided will give you the data transfer rate in bits per second. This is because the 800 MHz refers to the clock speed of the memory, which is measured in cycles per second. Each cycle can transfer one bit of data, so multiplying the clock speed by the number of bits (64) gives you the data transfer rate in bits per second.

To convert this to megabytes per second (MB/s), you would need to divide the result by 8, since 8 bits make up 1 byte. This would give you the data transfer rate in MB/s.

It is important to note that the data transfer rate of a memory module also depends on other factors such as the number of channels and the type of memory controller. So while this calculation will give you a rough estimate, the actual data transfer rate may vary.